ATP 2026 Heat Rule Explained: WBGT Thresholds, Cooling Breaks, and Winning Tactics

The rule changed. Preparation must, too.

Beginning with the 2026 season, the ATP will apply the Wet Bulb Globe Temperature, or WBGT, to manage extreme heat. When WBGT reaches 30.1°C during a best-of-three singles match, a supervised 10-minute cooling break can be taken after the second set. If WBGT crosses 32.2°C, play is suspended. The break can include hydration, clothing changes, a quick shower, and even coaching, all under medical supervision. These are not soft guidelines; they are hard thresholds that will dictate the rhythm of high-stakes tennis in hot months. You can read the key provisions in the official summary of the ATP heat rule for 2026. For a deeper breakdown of thresholds and match scenarios, see our full guide to ATP 2026 thresholds.

Why this matters now: in October 2025 at the Shanghai Masters, matches under heavy humidity and sun produced a wave of retirements and on-court distress. Players vomited, cramped, and questioned whether a formal standard existed. That week made the risk visible. The 2026 rule makes the response predictable.

WBGT in plain English

WBGT is not the same as the thermometer reading on your phone. It blends air temperature, radiant heat from the sun, humidity, and wind to estimate how hard the environment pushes your body to overheat. Two days with the same air temperature can have very different WBGTs. High humidity means sweat does not evaporate well. Full sun means more radiant heat. Low wind means less cooling. WBGT captures all of that in a single stress number.

Here is a simple way to feel the thresholds:

• Around WBGT 30.1°C, exertion feels sticky and relentless. Your jersey stays wet, your heart rate climbs sooner, and decision making slows. Ten minutes of deliberate cooling can drop core temperature and restore clarity.
• Above WBGT 32.2°C, the risk of heat illness spikes, even for fit athletes. That is why competition stops.

For coaches and parents without a WBGT device, use a practical checklist. If the sun is strong, humidity is above 70 percent, and there is little wind, treat any day above 86°F as a high-risk session. Schedule around it or reduce the load.

Shanghai 2025 was a warning shot

Shanghai’s hard courts played through heat and heavy humidity in early October 2025. Several players retired, multiple stars took medical timeouts, and cameras caught veterans leaning on towels between points. The tennis looked different. Rallies got shorter. Service patterns narrowed. Players who normally sprint to the line walked. That tournament became the case study that moved policy from discretion to threshold.

Turning thresholds into a plan

Rules do not win matches. Routines do. Build a routine around five pillars that map directly to the new rule: acclimation, pre-cooling, fueling, breathing, and gear.

1) Heat acclimation timeline that works

Goal: teach the body to sweat earlier, sweat more efficiently, and maintain plasma volume so heart rate does not spike.

• Days 1 to 3: 20 to 30 minutes of easy to moderate work in the heat, ideally in late morning or early afternoon. Shadow swings, footwork ladders, and light rallying. Finish with 10 minutes of easy bike or walk in the sun.
• Days 4 to 6: 40 to 60 minutes with interval structure. Example: 6 sets of 5-minute rally games at about 70 percent effort, 2 minutes rest with shade and sip. Observe how quickly you cool during rest.
• Days 7 to 10: Full sessions at normal intensity, but cut total volume by 15 to 20 percent compared to a cool day. Add a short match tiebreak at the end.
• Days 11 to 14: Return to normal volume. Insert one or two heat-specific match plays each week.

How to monitor: weigh in before and after each session, with shorts only, and track fluid change. Every 0.5 kilogram lost is roughly 500 milliliters of sweat. If you consistently lose more than 2 percent of body mass, increase fluids and sodium before and during sessions, or reduce load.

Acclimation is not permanent. If you leave the heat for two weeks, schedule at least 4 acclimation days on return. For a step-by-step build, use our 10-day acclimation plan.

2) Pre-cooling that actually lowers core temperature

Pre-cooling buys heat storage capacity. The body starts cooler, so it takes longer to reach the point where your brain forces you to slow down. The evidence base is strongest for cold water immersion, but that is rarely practical on site. The two match-day tactics that scale are an ice vest and an ice slurry.

• Ice vest: wear 15 to 25 minutes in the locker room before warm-up. Take it off to move, then put it back on for 5 minutes before walking to court.
• Ice slurry: blend crushed ice and a low-acid sports drink into a slush; aim for 300 to 500 milliliters in the 20 minutes before walking to court. Sip, do not chug. For smaller juniors, reduce volume. Avoid mixing with dairy if nausea is a problem.

A recent review summarizes that pre-cooling improves endurance performance in the heat, with external cooling often outperforming internal methods and combinations sometimes helping. See the peer-reviewed 2024 meta analysis on pre cooling for method choice and effect sizes.

During changeovers, use micro-cooling: ice towels on the neck and forearms, a quick splash on the crown of the head, a chilled grip towel. In hot, humid conditions the goal is conduction and convection, not evaporation. Think cold surfaces touching skin and moving air.

3) Smarter electrolyte fueling, not just more bottles

The target is to prevent large swings in plasma volume and maintain nerve conduction. Translate that into numbers you can coach.

• Pre-match: 500 milliliters of fluid with 600 to 800 milligrams sodium in the 60 to 90 minutes before walk-on, plus another 250 milliliters with 300 to 400 milligrams sodium 15 minutes before warm-up. Split into small sips.
• During play: 400 to 800 milliliters per hour for most players, up to 1 liter per hour for heavy sweaters. Sodium 500 to 900 milligrams per liter, higher if you see white salt marks on clothing or stinging eyes from salty sweat. Include 30 to 60 grams of carbohydrate per hour when matches exceed 90 minutes. Rotate flavors to prevent palate fatigue.
• Post-match: replace 125 to 150 percent of weight lost within 2 to 3 hours; include a salty snack or a sodium-containing recovery drink to hold the fluid.

DIY mix for the field: in 1 liter of cold water add 60 grams of table sugar, 3 grams of sodium citrate or 1.5 grams of table salt, plus a splash of citrus for taste. This gives a roughly 6 percent carbohydrate drink with around 600 milligrams sodium.

Red flags: pounding plain water for hours, muscle twitching, headache, or bloating. Those can signal too little sodium relative to fluid. On the other side, if urine stays dark and you feel nauseous, you are behind on fluids. Coaches should help athletes practice fueling during long training blocks, not only on match days.

4) Between-point breathing to control heart rate

The time rule gives you up to 25 seconds between points. Use it.

• Two slow breaths with a long exhale: inhale through the nose for 4 seconds, purse lips and exhale for 6 to 8 seconds. The long exhale tells the nervous system to shift toward recovery.
• One reset breath between first and second serve on big points: a quick 2-second inhale, a 4-second exhale, eyes on the strings, one cue word like loose.
• During changeovers: four cycles of 4 in, 6 out while you cool neck and forearms. Sit tall, shoulders down. Avoid slumping; it restricts ventilation.

Coaches can train this in drills: rally to 11 with a heart rate target, then test how many long-exhale breaths bring the player back to 120 to 130 bpm in 60 seconds. Make breath control part of the score.

5) Gear choices that reduce thermal load

• Clothing: light colors, micro-mesh fabrics, looser torso fit for airflow. Pack two extra tops and rotate every three to five games in humid conditions.
• Hats and headbands: a ventilated cap with a dark underbill to reduce glare, plus two dry headbands to rotate. A wet headband that no longer evaporates is dead weight.
• Shoes and socks: breathable uppers; thin technical socks under a second thin pair can reduce blisters from soaked fabric. Change socks at the mid-match cooling break if it happens.
• Grips and towels: overgrips that stay tacky when wet, plus a small chilled towel for the handle. Bring two wristbands and rotate.
• Sunscreen: broad spectrum, sports specific, applied at least 20 minutes before warm-up. Reapply at the cooling break if needed.

Tactics for matches that hit the threshold

The 10-minute cooling break after the second set creates a new hinge in three-set matches. Plan for it. For specific scenarios and coaching scripts, study our cooling break playbook.

• If you win the first set and the WBGT climbs, manage the second set to minimize core temperature. Shorten points with first-strike patterns, do not chase low-percentage passes, use body serves that come back to you. Aim to arrive at the break with confidence and reserves.
• If you lose the first set, choose whether to surge early in the second to level quickly, or conserve and reset for a full push after the break. The decision depends on opponent fitness signs. If they bend at the waist between points, slow their serve rhythm with legal towel walks and let the heat do work.
• Serve tempo: keep your routine, but remove any nonessential bounces or twirls to save seconds for breathing. Use more body serves and wide targets to cut off the first ball. Accept a slight first-serve percentage drop if it produces shorter points.
• Return positioning: step back a half step to buy time when legs feel heavy, especially against big servers. Against slower serves in extreme heat, cheat in and chip deep to the middle to limit running.
• Rally patterns: bias to crosscourt and through the center to reduce court coverage. Slice backhand to take pace off and gain recovery. If your opponent crowds the baseline in heat, lift higher crosscourt and watch them move back.

Using the cooling break for coaching

The rule allows coaching during the cooling break, under supervision. Treat it like a two-minute pit stop, just longer.

Checklist for the 10 minutes:

1. First 90 seconds: sit, ice towel on neck and forearms, sip a saline drink, two long-exhale breaths.
2. Minutes 2 to 4: quick shower or full shirt change, fresh socks if needed, swap to a dry grip. Put on an ice vest if available.
3. Minutes 4 to 6: coach conversation in the shade. One tactical focus, one serving pattern, one return cue. Keep language simple and positive. Example: serve body on ad, first ball to backhand through the middle.
4. Minutes 6 to 8: carbohydrate mouth rinse or small sip, visualize first two points after the break, rehearse breathing.
5. Minutes 8 to 10: stand, two practice swings, a final long exhale, walk to court organized and unhurried.

String tension note: in heavy humidity the ball can feel heavier off the strings. If you have a second frame, go down 1 to 2 pounds for free depth, but only if you tested it in practice.

What this means for club players and juniors

Even without an official WBGT monitor on your court, the new standard should drive how you plan practice and matches.

• Schedule: when forecast humidity is high, move hard sessions to morning or late afternoon. Use the hottest window for low-intensity technical work or serve practice with long rests.
• Match play: set a house rule that at perceived WBGT 30+ you add two minutes of cooling whenever a set ends. Teach players to treat that time like the pro-level break.
• Tournament directors: post a simple heat policy on the draw desk. State how you will add shade, where ice towels live, and how you will stagger match starts if conditions spike.
• Parents: pack a small cooler with ice bags, a shaker for slush, extra clothing, and two labeled squeeze bottles so your player can switch without thinking.

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. Use it to build a two-week acclimation block, to schedule pre-cooling practice sessions, and to train between-point breathing in realistic rally intervals.

A week-by-week action plan for 2026

Four weeks out

• Confirm travel dates and likely hot tournaments on your calendar.
• Start a twice-weekly heat exposure session if you live in a cooler climate. Treadmill or bike in a warm room can help. Keep sessions short and controlled.
• Test your fueling. Mix two strengths of sodium and find the one that leaves you clear headed, not bloated.

Two weeks out

• Begin the full 10 to 14 day acclimation protocol. Track body mass and sweat rate.
• Acquire or test your ice vest, blender technique for slush, extra grips, and towel rotation system. Practice the pre-match sequence.

One week out

• Simulate a hot three-set match. After two sets, take a 10-minute cooling drill using the exact checklist you will use in competition. Practice coach communication in short, clear bursts.
• Finalize string tensions for humid days versus dry heat days. Pack both.

Tournament week

• Two days before first match: reduce total practice volume by 20 percent, keep intensity sharp, keep pre-cooling routine.
• Match day: execute the pre-cooling protocol, set drink volumes on court, and rehearse breathing cues during warm-up. Play the chess game of tempo and court position, not just the ball.

The most important habit of all

The athletes who will thrive under the 2026 rule will not be the ones who tolerate heat best by nature. They will be the ones who take heat seriously as an opponent and train against it with the same attention they give a lefty serve. Measure. Rehearse. Adjust. Then do it again.

Open your calendar and block two acclimation weeks before your first hot event. Share this article with your player or coaching staff. Build your cooling checklist and drill it in practice. If you want a guided plan with breathing drills, fueling calculators, and acclimation sessions that match your playing style, start a program in OffCourt today and turn the new rule into a competitive edge.