The heat rule that will change match chess
In December 2025 the ATP approved a new extreme heat policy that will take effect for the 2026 season. The rule uses the Wet Bulb Globe Temperature, a composite measure of heat stress. When the WBGT hits 30.1 degrees Celsius during the first two sets of a best-of-three singles match, either player may request a supervised 10-minute cooling break after the second set. If the WBGT exceeds 32.2 degrees Celsius, play is suspended. Players may shower, change, hydrate, and receive coaching during the break. That is the plain language version of the official announcement, which is worth reading for the exact thresholds and scope in the ATP announcement on new heat rule. For a deeper thresholds explainer, see our ATP 2026 WBGT thresholds guide.
For juniors, coaches, and parents, this is not just an athlete safety story. It is a tactics story and a preparation story. The smartest teams will treat the 10-minute break as a controllable performance window. The smartest programs will train for that window months in advance.
WBGT in simple terms
WBGT blends temperature, humidity, sun exposure, and wind into one number that predicts heat stress. Think of it like the speed limit on a highway that is set not only by road quality but also by rain, fog, and traffic. When the number passes a certain mark, the speed limit drops. In tennis, once WBGT reaches 30.1 in the first two sets, the break becomes available. Above 32.2, the match stops.
Two important clarifications for planning:
- The break applies only in best-of-three singles. It does not create a mid-match pause in doubles or best-of-five.
- The break happens after set two. If the threshold is reached in set one or two, the pause is after set two. If WBGT climbs during set three, there is no break. That timing shapes how you manage momentum and energy across the first two sets.
Momentum management: choosing when to pull the lever
Because either player can request the break, it will become a strategic lever. Use these scenarios to guide the decision.
- You win set one and the WBGT is flirting with 30.1 late in set two. If set two turns into a tug-of-war, consider banking the break to disrupt the opponent’s push. The goal is to protect the one-set lead and reset your legs for the decider.
- You lose set one but pull even in set two. If the second set is close and the WBGT qualifies, request the break to puncture the opponent’s momentum and to reframe the match as a fresh sprint.
- You serve particularly well early in matches. If you expect a dip in serve speed from heat fatigue by set three, take the break when available to preserve serve quality for the stretch run.
One guardrail: do not chase the break at the expense of sound patterns. You cannot influence WBGT with shot selection, and overextending rallies to bring on a break often backfires through cramps or sloppy errors. Play within your identity and treat the break as a bonus reset, not a rescue plan.
Serve and return pacing under heat stress
Heat does not just slow legs. It alters decision speed and fine motor control. Here is how to adapt.
Serving adjustments
- Reduce pre-serve rituals to the essentials. If you bounce the ball ten times, train a five-bounce routine for hot matches. You respect the 25-second clock while lowering your thermal load.
- Aim more at the body and the T when you tire. These targets shorten points and reduce lateral stress on your hips.
- Use heavier spin on second serves to buy recovery time without inviting attack. The goal is fewer double faults when your forearm feels glassy.
- After the break, script your first service game. Example: first point body serve to the ad court, second point wide slider in deuce, third point T serve in ad. Pre-planning reduces indecision when your brain is cooling and needs structure.
Returning adjustments
- Stand half a step farther back on second serves when legs are heavy. It gives a fraction more time for a compact swing.
- Pick one forehand and one backhand return pattern for the first two return games after the break. Example: chip backhand crosscourt; forehand block middle. Simple beats clever when your hands are cold from a shower and the racquet feels different.
Between-point routines
- Use the towel and deep belly breathing on every point change. Inhale through the nose for four counts and exhale for six to shift toward parasympathetic recovery.
- Keep shade discipline. Move to the shadow of courtside umbrellas or signage between points. The difference in radiant heat is real.
- Assign grips and strings to the bench. Regrip early if sweat saturation is high. A fresh overgrip at 4-all can save a tiebreak.
The 10-minute cooling break: a minute-by-minute playbook
Treat the break as a pit stop. Every second must have a job. For a printable version, grab our cooling break playbook checklist.
- Minutes 0 to 2: Walk briskly off court. Unlace shoes slightly to reduce foot pressure. Remove saturated shirt and wristbands.
- Minutes 2 to 4: Cold water over forearms and neck. If available, use an ice vest. Lightly fan to enhance evaporation.
- Minutes 4 to 6: Drink a measured bottle. Target a mix that matches your sweat profile. For most athletes, a drink with both carbohydrate and sodium beats water alone. Avoid chugging to prevent stomach slosh.
- Minutes 6 to 7: Bathroom if needed. Quick shower if facilities allow. Pat dry, not rub, to preserve skin comfort under tape.
- Minutes 7 to 8: Coaching huddle. One tactical priority for serve games, one for return games, and one emotional cue. Keep it on a notecard.
- Minutes 8 to 9: Regrip, re-tape fingers if prone to blisters, apply new wristbands. Confirm string tension feel by three shadow swings.
- Minutes 9 to 10: Eyes closed. Rehearse the first game plan. Step out with a crisp walk and neutral face.
Pro tip: practice the break in training. Time it. Rehearse the order. The best teams will make this flow automatic, the way a Formula One crew choreographs a tire change.
Hydration and cooling upgrades that actually move the needle
A good plan begins before the match and continues after it.
Before the match
- Prehydrate two to three hours out with a measured bottle. Include sodium, especially for salty sweaters who see white streaks on hats and shirts.
- Cool the core. An ice slurry or cold smoothie 30 to 45 minutes before warmup can lower starting body temperature and delay the point where heat becomes limiting.
- Prep your kit. Two extra shirts, two extra overgrips, a small chamois towel, and a labeled drink for each set. Labeling avoids guessing when fatigue fogs memory.
During the match
- Drink by plan, not by thirst alone. On a hot day, aim to limit body mass loss across the match. Weigh before and after practice days to learn your sweat rate so you can build a personalized plan.
- Use evaporative cooling. A damp towel on forearms between points plus a fan at changeovers enhances heat loss.
- Guard the gut. If you cramp or feel bloated in heat, reduce concentrated gels and distribute carbohydrate through sips.
After the match
- Replace fluids and sodium according to post-match weight loss. A rough guide is one and a half liters of fluid for each kilogram lost over the next several hours, with sodium included.
- Prioritize a cool environment, light protein and carbohydrate meal, and gentle mobility. A long ice bath is optional and should be tested in training to ensure it does not make you feel sluggish.
Simulating heat before the Australian summer
You do not need a chamber to acclimate. You need a plan. The Australian swing has long days, strong sun, and hard courts that radiate heat. This is how to build a block that raises your heat tolerance and protects your engine. Build your two-week block with our 10-day WBGT acclimation plan.
Two-week ramp, then sharpen
- Days 1 to 3: 45 to 60 minutes of steady on-court hitting in the hottest safe part of the day for your location, or indoors with less airflow if weather is mild. Keep heart rate moderate. Finish with 15 minutes of light footwork circuits. Hydrate with sodium. Record body mass before and after.
- Days 4 to 7: 60 to 75 minutes on court with short live points. Add a 10-minute mid-session cooling drill to mimic the ATP break. Walk to shade, towel forearms, sip a measured drink, receive a one-minute coaching cue, then restart with two scripted games.
- Days 8 to 12: 75 to 90 minutes including set play. Schedule the simulated break after set two no matter the score. Practice the minute-by-minute pit stop plan. Track how your first two games after the break feel and how your serve speed and double faults change.
- Days 13 to 14: Taper volume by 20 to 30 percent. Keep intensity with short point games. Practice arriving hot and starting fast with a focused warmup sequence.
If you have access to a safe sauna protocol, some players add short, supervised post-training heat exposures. Always test this months before the season, not in the week of a tournament.
Australian Open policy context
Grand Slams set their own heat rules. The Australian Open uses a Heat Stress Scale that blends environmental measures into a five-level dashboard and includes planned breaks and potential suspension when the scale peaks. If you or your player are heading to Australia, learn that system through the Australian Open heat policy explainer. Understanding both the ATP thresholds and the Melbourne Park routine reduces surprises when the January sun arrives.
Coaching logistics that win tight matches
- Forecast the day. Build a simple WBGT and air temperature tracker in your match plan. If the forecast suggests a qualifying WBGT window during the first two sets, prepare your athlete for the break.
- Pack the bench. Ice towels in a soft cooler, spare shirts in zip bags, pre-labeled bottles, a small fan where allowed, sunscreen, spare socks, and a written 10-minute checklist. Chaos is the enemy of recovery.
- Define roles. One coach monitors match tactics. One support person tracks time during the break, hands the next item, and keeps the area calm. If you coach juniors, assign a parent as the logistics lead at summer events.
- Rehearse communications. Use short cues. Example: Serve body ad. Return chip backhand cross. Breathe four-six. Long speeches waste cooling time.
What will change tactically in 2026
- More decisive third sets. Cooler bodies and clearer heads after the break should raise the quality of deciding sets. Expect fewer crumble-outs and more tactical accuracy.
- Slightly slower early-third-set pace. Many players will simplify patterns for two games after the break while hands re-warm. Smart returners will attack early second serves in that window.
- Higher value on fitness that resists heat. Players who can keep footwork and decision speed intact to 4-all in the third will gain ranking points at hot events.
- Coaching becomes a moment of leverage. Because coaching is allowed during the break under supervision, the best teams will turn ten minutes into a full reset of patterns and emotion.
Common mistakes to avoid
- Overcooling. An ice bath effect without re-warming the hands can make the first two games after the break feel clumsy. Dry hands, fresh overgrip, and three shadow swings matter.
- Drinking only water. Heavy sweaters need sodium. Learn your sweat profile in practice, not on match day.
- Treating the break as a spa stop. It is a reset for performance, not a reward. Every item in the ten minutes must have a purpose.
How OffCourt can help you operationalize this
Off-court training is the most underused lever in tennis. OffCourt unlocks it with personalized physical and mental programs built from how you actually play. Inside OffCourt.app you can:
- Build a two-week heat acclimation block that fits your schedule and environment. The plan can include simulated breaks and minute-by-minute routines.
- Generate hydration guides based on your training logs. The app learns when you tend to cramp or fade and recommends specific adjustments.
- Script your post-break playbook by match identity. If you are a serve-first player, the app nudges a different restart plan than for a counterpuncher.
For more tactical detail, see our ATP cooling break tactics guide.
The bottom line and your next steps
The ATP’s WBGT rule, approved in December 2025 and live for 2026, gives players a defined, coachable 10-minute window that will swing matches. The teams who treat that window like a pit stop, and who train for heat like a skill, will win more deciding sets in January and beyond.
Your action plan this week:
- Time and rehearse a 10-minute cooling routine with your coach. Treat it like a set piece play.
- Weigh in and out of two hot practices to estimate sweat loss and build a personalized hydration plan.
- Schedule a two-week heat simulation block before your summer events. Include at least three full break rehearsals.
- Save your script in OffCourt.app so your plan travels with you.