Guide
Australian Open format explained: heat, roofs and January
The Australian Open format from the inside: the five-level heat stress scale, three roofed arenas, and what going on first actually costs players.
By CricketTaken EditorialPublished Guide18 min read
Play is running on twelve courts at Melbourne Park when a number on a screen in the referee's office ticks past 5.0. Within minutes the outside courts are emptying, the roofs on three arenas are sliding shut, and a tournament that was fully outdoors becomes an indoor event without the schedule losing a match. Nowhere else in tennis can do that, and the Australian Open format explained below is largely a story about what a venue built for extreme heat allows an organiser to do.
The basics first. The Australian Open is the year's first major, held over fifteen days in the middle of January at Melbourne Park on cushioned acrylic hard courts. Both singles draws hold 128 players, with 104 direct entries, sixteen qualifiers and eight wildcards. Men play the best of five sets and women the best of three, and a deciding set that reaches six games all is settled by a tie-break to ten points. Three arenas have retractable roofs, and an extreme heat policy graded from one to five governs when play stops.
Everything else that makes this tournament distinct falls out of two facts: it is played in an Australian summer, and it is played before anyone is ready.
The heat problem, and the three answers Melbourne tried
Melbourne's January weather is not merely hot. It is volatile, capable of swinging by fifteen degrees in an afternoon when a southerly change comes through, and capable of sitting above forty degrees for several consecutive days. A tournament running eleven hours a day for a fortnight cannot treat that as an exception.
The first answer, adopted in 1998 after players pushed for one, was a fixed threshold: play stops at 40 degrees Celsius. That number moved twice in the following years, down to 38 and then to 35, with a wet-bulb globe temperature measure added alongside it.
The problem with a fixed threshold is that air temperature is a poor description of heat stress. A body sheds heat by evaporating sweat, and evaporation slows when the air is already humid. It also gains heat directly from the sun, which a shaded thermometer does not see. So 33 degrees in still, humid, cloudless conditions can be more dangerous than 38 degrees with a breeze and cloud, and a rule keyed to one variable will be wrong in both directions.
The second answer, from 2015, tried to patch this by raising the temperature trigger to 40 and the wet-bulb measure to 32.5, and by allowing matches to halt after complete games rather than at the end of a set. That was an improvement in mechanics and not in measurement.
The third answer, in place since 2019, threw out the thresholds altogether.
How the AO Heat Stress Scale works
Tennis Australia's medical staff built the current index with the Thermal Ergonomics Laboratory at the University of Sydney, and it works from four climate inputs rather than one.
Those inputs are air temperature measured in the shade, radiant heat from the sun, relative humidity, and wind speed. They are combined into a single figure on a scale from 1.0 to 5.0, and they are measured continuously at several positions around the precinct, including on the courts inside Rod Laver Arena, Margaret Court Arena and John Cain Arena rather than only at a weather station on the roof.
The reason the readings are taken on court matters. A stadium bowl with dark surfacing behaves differently from open ground: it stores radiant heat during the day and releases it, and it blocks the wind that would otherwise carry heat away from a player. A number taken at the boundary of the site would systematically understate what a player standing on the baseline is experiencing.
The scale also distinguishes between the people playing on it. Tennis Australia's chief medical officer has described it as built around the maximum heat stress an athlete can safely tolerate, their sweat rate and their core temperature, and it is calibrated separately for adults, junior players and wheelchair athletes. A wheelchair player has a smaller effective surface area for cooling and less capacity to shed heat through the legs, and a fourteen-year-old in a junior draw is not physiologically an adult. A single trigger applied to all three would be too lax for two of them.
- 111500000Total prize money, Australian dollars
- 4150000Singles champion, each draw
- 3Courts with a retractable roof
- 5Levels on the heat stress scale
Published figures for the 2026 edition and the current site configuration. Prize money and attendance are revised annually.
What actually happens at each level
Levels one to three are ordinary tennis. Cooling aids are available, ice and shade are provided at changeovers, but the schedule runs as written and nothing about the match format changes.
Level four is where the rules move. Extended breaks between sets become available: ten minutes for women's and junior singles players after the second set, ten minutes for men's singles players after the third, and fifteen minutes for wheelchair singles players. Play continues on every court, including the outside ones, and the break is an entitlement rather than a suspension.
Level five is a stop. The referee can suspend the start of matches on outdoor courts and can halt matches already in progress, taking them off after an even number of games or at the completion of a tie-break so that neither player is caught mid-game with an unequal number of service games. Matches on the three arenas continue, because their roofs can be closed and their interiors are air conditioned.
That last clause is the whole point of the system. At the other majors an extreme heat call is a straightforward loss of playing time. Here it is a transfer: the tournament loses the outside courts and keeps the three biggest, which between them can carry a substantial programme. A Melbourne day that would shut down anywhere else keeps producing the matches that matter most to broadcasters and ticket holders.
- Sensors report from five positionsAir temperature in the shade, radiant heat, humidity and wind speed are measured continuously around the precinct, including on court inside the three roofed arenas.
- The four inputs become one numberThe readings are combined into a single figure between 1.0 and 5.0, calibrated separately for adult, junior and wheelchair athletes.
- Below four, nothing changesCooling aids and changeover provisions apply, but the programme runs as scheduled on every court in use.
- At four, extended breaks open upWomen and juniors may take ten minutes after the second set, men ten minutes after the third, and wheelchair singles players fifteen. Matches continue everywhere.
- At five, the referee suspends outdoor playNew matches are held back and matches under way come off after an even number of games or at the end of a tie-break.
- The roofs close and the arenas keep goingRod Laver, Margaret Court and John Cain continue under cover with air conditioning, so the headline programme survives the suspension.
- Play resumes when the reading fallsOutdoor matches restart from the score at which they stopped once the referee is satisfied the conditions have eased.
The sequence set out in Tennis Australia's published extreme heat protocols. The tournament referee holds every decision.
Three roofs, and who decides
Melbourne Park has more covered capacity than any other Grand Slam venue, and it acquired it in three stages across three decades.
Rod Laver Arena opened with the site in 1988 and carried a retractable roof from the start, the first at any major. John Cain Arena, which has gone through several names, opened in 2000 with a roof of its own. Margaret Court Arena was rebuilt and gained one for the 2015 tournament. A fourth show court, Kia Arena, opened in 2021 with about 5,000 seats and no roof.
The operating rule is the same one the other majors use, and it exists to protect fairness rather than comfort. The referee alone decides whether a roof closes, and once a match is running in a given configuration it finishes in that configuration. A player cannot ask for the roof, and a match that started outdoors does not move indoors because one competitor is losing.
The difference between the two states is not cosmetic. A closed arena is still, warm and dry, with no sun to contend with on the ball toss and no breeze to move a lob. Serving is easier, flat hitting is more reliable, and the court plays quicker because the ball keeps its bounce. A player who arrives at the semi-final stage having played four matches under a roof and one outdoors has effectively played two different tournaments.
Four surfaces in one century
No other major has changed what it is played on this often, and each change tells you something about the tournament's priorities at the time.
The championship was played on grass until 1987, at a rotation of venues around Australia and latterly at Kooyong in Melbourne. Grass in an Australian summer is a difficult proposition: it dries out, wears through at the baseline within days, and produces bounces that get less predictable as a fortnight goes on.
The move to Melbourne Park in 1988 brought Rebound Ace, a cushioned synthetic hard court. It was popular initially because of what it did for players' joints, and unpopular later because of what heat did to it. The surface softened in extreme temperatures, which made it grabby underfoot and inconsistent in bounce, and the injury complaints eventually became loud enough to matter.
Plexicushion arrived for 2008. It was a thinner build, which meant it retained less heat, and it played slightly quicker with a more uniform rebound. It lasted twelve years.
GreenSet has been the surface since 2020, another cushioned acrylic system, and it kept the same blue playing area and green surround. That colour continuity is why the last two changes passed most viewers by entirely.
The playing consequences of the whole sequence run in one direction. The tournament has moved from an unpredictable natural surface to a specified synthetic one, and from a surface that misbehaved in heat to ones that do not. What has not changed much is speed: the Australian Open sits in the medium range of hard courts, quicker than clay, slower than an indoor carpet, and close enough to the US Open that a player who does well at one usually does well at the other. The wider mechanics of how a surface sets bounce and pace are covered in the explainer on what actually differs between court surfaces.
The criticism the heat policy still attracts
A five-level scale built with a university laboratory is a serious piece of work, and it has not stopped the argument. Three objections come up every January and each has something in it.
The first is that the number itself is not published live. Spectators and players see the consequences of a reading rather than the reading, and a decision that looks arbitrary from the stands would look less arbitrary if the figure were on the scoreboard. The tournament's position is that the calculation is complex and that a raw number without context invites misreading, which is true and also convenient.
The second is that level four does nothing for the player in trouble during the first set. A break between sets is relief that arrives on a schedule rather than when it is needed, and a competitor who is struggling at four games all in the opening set has only the changeover. The counter is that stopping a match at any point on demand would hand a tactical weapon to whoever is losing.
The third is the fairness of the transfer at level five. When outdoor play is suspended and the three arenas keep going, the players on those arenas continue in air conditioning while everyone else waits, sometimes for hours, and then restarts in a compressed schedule. That is a better outcome than shutting the whole site down, and it is still an unequal one. A tournament with three roofs has more options than any of its peers and is therefore more visibly making choices about who gets which conditions.
None of this makes the scale a failure. It replaced a rule that keyed everything to a thermometer reading with one built on how bodies actually shed heat, and that is a genuine improvement. What it cannot do is make a January fortnight in Melbourne comfortable.
Going first, and what that costs
The Australian Open is the first major of the year, and it is the only one that has to be won by players who have barely played.
The professional season finishes in November, and the tournament starts in the middle of January. That is the shortest gap between any two majors on the calendar, and it has to contain a genuine off-season, a pre-season training block, travel to the southern hemisphere and whatever match play a player can find. Most arrive having played one or two lead-in events over a fortnight, against opponents in the same condition.
Three things follow.
Form is unreadable in the first week. A player's ranking reflects the previous twelve months, and the previous twelve months ended six weeks ago in different weather on a different continent. Seeds lose early here more often than a bracket would suggest, and the reason is preparation rather than pressure. The way rankings and seeding interact is set out in the guide to how seeds are placed in a Grand Slam draw.
Physical readiness is the real variable. Best-of-five tennis in Melbourne heat, four or five days into a fortnight, is the hardest physical test in the sport, and a player who used December to rest rather than to train will find that out in the third round. Injuries carried out of the previous season have had less time to heal here than anywhere else.
The lead-in is thin. The southern hemisphere swing is short and geographically scattered, and a player choosing between match practice and a training block is making a real trade rather than a false one. The reasons the calendar has this shape, and why it resists being changed, are set out in the piece on how the tennis year is assembled.
The expansion into a multi-week event
From 2024 the main draw moved its start from Monday to Sunday, making the Australian Open a fifteen-day tournament and spreading the first round over three days rather than two.
The stated reason was late finishes. Matches have got longer, and a first round compressed into two days had been pushing play deep into the night on the show courts, which is bad for players and bad for anyone trying to get home. Spreading the round wider gave the schedulers room to end sessions at a sensible hour.
The commercial effect came with it. The change raised the number of sessions on the three roofed arenas from 47 to 52, which is five more ticketed events in the venues that generate the most revenue. Tennis Australia was straightforward about both motives.
The expansion sits on top of a longer trend. Melbourne Park is now busy for weeks either side of the main draw: qualifying, the wildcard play-offs, junior and wheelchair events, exhibition matches and a large public festival occupy the site, and the tournament has grown into something closer to a summer season than a fortnight. Attendance has followed, with more than 1,360,000 people through the gates across the 2026 edition including the qualifying rounds, which is the largest figure any major reports.
Whether fifteen days actually solved the late-finish problem is a fair question and the evidence is mixed. Adding a day helps the first round; it does nothing for a five-set quarter-final that starts at nine in the evening because a women's match in the same session went to three sets. The structural fix would be scheduling fewer matches per session, and that costs money the expansion was designed to earn.
Getting in: qualifying, wildcards and the play-offs
The 128 places in each singles draw are filled the same way as at the other majors. Around 104 go to players high enough on the entry list when it closes, sixteen are won through a qualifying event on the site the week before, and eight are given out by the organisers.
Tennis Australia does something with its wildcards that the other majors mostly do not: it awards several of them through competition. A domestic play-off is staged in December, and the winners receive main-draw places. There is also an Asia-Pacific play-off, which gives a route to players from a region that is otherwise thinly represented in the rankings, and reciprocal arrangements exchange places with other federations so that an Australian can receive a wildcard elsewhere and a foreign player can receive one here.
That approach answers the standard objection to wildcards more convincingly than a straightforward gift does. A place won in a play-off has been earned in a competition, even if the field for that competition was restricted by nationality. It does not remove the discretion entirely, because some wildcards are still awarded directly, but it converts a chunk of the allocation from patronage into a result.
Qualifying itself is three rounds, played in the heat, on the same surface, in the days immediately before the main draw. A qualifier who comes through has won three matches in Melbourne conditions when their first-round opponent may have played none since November. In a tournament where preparation is the scarcest resource, that is worth more here than it is anywhere else on the calendar.
The crowd, and why the nickname stuck
Players have called this the friendly major for years, and the reasons are structural rather than sentimental.
The site is compact and walkable, sitting beside the Yarra a short stroll from central Melbourne, so a spectator can arrive by tram and be inside the grounds in minutes. There is no long approach through suburban traffic, and the show courts, practice courts and outside courts sit close enough together that a grounds pass buys a full day rather than a consolation prize.
John Cain Arena does something no other major show court does: a large part of it is sold as general admission on a grounds pass, which means a 10,000-seat roofed stadium fills with people who did not pay a premium and behave accordingly. The noise in there is closer to a football crowd than a tennis one, chants and all, and players either enjoy it enormously or ask not to be scheduled there.
The timing helps too. January in Australia is a holiday month, so the audience is not squeezing the tournament around a working day, and evening sessions in warm weather draw people who would not otherwise buy a ticket. The tournament has leaned into that with a music programme, food precincts and public screens outside the arenas, and the result is an event with a substantial audience that never watches a full match.
There is a business logic underneath the friendliness. An event that has to compete for attention against a crowded Australian summer sporting calendar cannot rely on tennis alone, and a festival that people attend for its own sake fills the site on days when the draw is thin.
The draws beyond singles
Doubles runs to 64 teams in the men's and women's events, best of three sets, with a portion of the field filled through its own qualifying competition. Mixed doubles is played inside the main draw here, which is now a point of difference: the US Open moved its mixed event out of the fortnight entirely and shortened it, while Melbourne has kept the traditional shape.
The wheelchair competitions run in the second week across men's, women's and quad divisions in both singles and doubles. The two-bounce rule changes the geometry of every rally, and the quad divisions, for players with impairment affecting three or more limbs, allow the racquet to be taped to the hand and permit electric chairs. Melbourne stages these on show courts rather than tucking them onto outside courts, and the scheduling decision is deliberate.
The junior championships fill the same stretch, and the site also hosts an event for former professionals and a range of exhibition matches. By the final weekend the singles draws need two courts, and the surrounding programme is what keeps a site of this scale in use.
The money, and where it goes
Total prize money for the 2026 edition reached A$111.5 million, with each singles champion taking A$4,150,000. Both singles draws are paid identically at every round.
The number that matters more for the health of the sport is the first-round figure. A player who loses their opening match at a major still collects a sum that would take a full season of results on the tour below to earn, and losing in the final round of qualifying pays enough to fund months of travel. That is the practical reason a wildcard play-off in December is contested as hard as it is, and why a qualifier who comes through three matches in Melbourne heat has changed their year before the main draw starts.
Prize money at all four majors has grown faster than inflation for more than a decade, driven by broadcast deals and by pressure from player groups arguing that the share reaching the early rounds is too small. The tournaments respond that they carry the cost of stadiums, roofs and a site that stands idle for most of the year, which in Melbourne's case is a stronger argument than it is elsewhere: three retractable roofs and a heat monitoring system are expensive things to own.
The scoring rules, and the one that arrived first
The Australian Open uses the standard Grand Slam scoring: best of five sets for men's singles, best of three for women's singles and for all doubles, with tie-breaks to seven points at six games all in every set except the last.
The deciding set is where the tournament led. From 2019 it introduced a ten-point tie-break at six games all in the final set, at a time when Wimbledon was adopting a tie-break at twelve games all and Roland-Garros was still playing final sets out with no limit. In March 2022 the governing bodies agreed a single rule across all four majors, and the version they chose was the one Melbourne had been using.
Electronic line calling has been in place across the courts for several years, with recorded calls and no line judges, and the shot clock governs the interval between points. Both changes push in the same direction as the fifteen-day expansion: a match that finishes closer to its scheduled slot.
What to watch for at a Melbourne fortnight
Check the roof before you judge the tennis. If a match is being played under a closed arena, expect quicker conditions, more free points on serve and fewer of the long defensive rallies that outdoor heat produces. A player who thrives in one state often struggles in the other, and the change can happen between rounds.
Watch the changeovers in the first week. Ice vests, towels packed with ice, players sitting for the full ninety seconds without moving: those are the signs the scale is high even before an announcement is made. If a ten-minute break is taken after the second or third set, watch what each player does with it, because the one who comes back moving freely has usually managed the recovery better than the one who comes back looking refreshed.
Watch the seeds in rounds one and two. Early exits are more common here than at the other majors, and the usual cause is a player who arrived without enough match play meeting someone who spent December on court. A qualifier or a play-off wildcard in that fixture is not the outsider the ranking gap suggests.
Watch the wind on the outside courts in the afternoon. Melbourne's southerly change can arrive during a match and swing conditions from still and baking to gusty and ten degrees cooler within half an hour, and a player who was serving comfortably into a dead sky suddenly has a ball toss to manage. Whoever adjusts their toss and their margins first usually takes the next two service games.
Watch how the court behaves late in the second week. A hard court does not degrade the way grass or clay does, but the baselines lose grit under two weeks of sliding and scuffing, and the bounce out wide can differ from the bounce down the middle by enough to matter on a stretched forehand.
Watch the depth of the returns in a night session on Rod Laver. Cooler evening air and a closed or partially shaded arena reduce how far the ball carries, so returners who were blocking serves back at midday start driving them, and a server who dominated an afternoon match can find the same delivery coming back at their feet after dark.
The Australian Open is the major that decided to engineer its way out of its own climate, and the engineering shows in every part of the format: three roofs, a five-level scale built with a university laboratory, a surface changed four times, and a fortnight stretched into something closer to a season. It goes first, and it asks players to be ready before anyone is. For the surfaces, the calendar and the rules that sit behind all of it, the rest of our tennis coverage has the detail, and every explainer we have written is on the blog.
Common questions
What is the Australian Open Heat Stress Scale?
It is a five-level index that combines air temperature in the shade, radiant heat from the sun, humidity and wind speed into one number between 1.0 and 5.0. Tennis Australia's medical team built it with the University of Sydney's Thermal Ergonomics Laboratory, and it replaced fixed temperature triggers from the 2019 tournament. Readings are taken continuously at several positions around Melbourne Park, including on the main show courts.
When does the Australian Open stop play for heat?
At a reading of 5.0 the tournament referee can suspend the start of matches on outdoor courts and halt matches already under way, taking them off after an even number of games or at the end of a tie-break. Play continues on the roofed arenas because those roofs can be closed. At level four, one step below, play continues everywhere but extended breaks between sets become available.
How many Australian Open courts have roofs?
Three. Rod Laver Arena has had a retractable roof since Melbourne Park opened in 1988, John Cain Arena since 2000, and Margaret Court Arena gained one in 2015. That gives the tournament more covered capacity than any other major, which is why a Melbourne programme can keep running through weather that would stop the others.
What surface is the Australian Open played on?
A cushioned acrylic hard court, branded GreenSet since 2020. The tournament was played on grass until 1987, then Rebound Ace from 1988 to 2007, then Plexicushion from 2008 to 2019. The colour has stayed blue through the last two changes, which is why the switches went largely unnoticed by viewers.
How long is the Australian Open?
Fifteen days since 2024, when the main draw moved its start from Monday to Sunday. The change spread the first round across three days and increased the number of sessions on the three roofed arenas from 47 to 52. Qualifying and the lead-in events run in the weeks before that, so the Melbourne Park site is in use for much longer than the main draw.
Why is the Australian Open the hardest major to prepare for?
It falls in the middle of January, only a few weeks after the previous season finished, so the off-season that precedes it is the shortest gap between any two majors on the calendar. Players arrive with limited match play, on a surface and in heat that punish anyone underprepared, and the lead-in events are few and short. Early-round upsets are more common here than at the other three majors for that reason.
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