US Open 2025 Heat Playbook: Checks, Cooling, Pacing

Why this matters now

The heat was a real opponent at the US Open 2025. The USTA added shaded rest areas and misting stations on outer courts because the heat index spiked. At least three main-draw matches saw medical timeouts for cramping or heat illness in week one. IBM noted longer rallies and higher point duration on hot afternoons, which meant higher heart-rate load and more drift in decision making.

This playbook is the field kit I now give competitive juniors and adult league players heading into late-summer events. It is short on theory and long on what you can do at a changeover with a towel, a cooler, and two minutes. I will flag where OffCourt can help you track and plan.

Field notes from NYC

• Shaded rest and misting stations expanded across outer courts.
• Several medical timeouts for heat issues in week one.
• Afternoon sessions saw longer rallies and higher heart-rate load.

What heat does to your match

• Raises core temperature. Your body diverts blood to the skin to cool, which can reduce power and focus.
• Slows your between-point reset. You spend more of the 25 seconds just getting back to baseline.
• Nudges errors late in games. Decision fatigue climbs when hot.
• Extends rallies. Higher bounce and kick change court spacing and point DNA.

Your plan must do two things: check risk fast, and cool you fast. Then pace wisely.

The two-minute on-court heat check

Run this at every changeover in hot matches. It takes less than two minutes. You can do parts of it between points with practice.

1. Orthostatic heart-rate check (40 seconds)

• Sit for 20 seconds. Note heart rate on your watch or neck pulse.
• Stand. After 20 seconds standing, check again.
• Delta guide: +0 to +15 bpm is manageable. +16 to +25 bpm means caution. More than +25 bpm means you must cool and slow pace.

2. Cognitive snap test (10 seconds)

• Name your next two patterns out loud: serve target + first ball. Or return contact height + recovery lane.
• If you hesitate or change your mind, you are hot and fuzzy. Default to simple patterns.

3. Thirst and mouth feel check (10 seconds)

• Dry mouth and sticky saliva mean you are behind. Plan to drink more this and next changeover.

4. Sweat salt check (10 seconds)

• Look for salt crust on forearms or hat band. If visible, plan higher sodium next changeover and post set.

5. Quick urine color check when you take a bathroom break between sets

• Pale straw to light yellow is good. Dark yellow to amber means you are behind.

6. Body mass loss snapshot

• Use a small travel scale pre-match in the locker room and post-match. Aim for less than 2 percent body mass loss. If you drop more, you under-fueled fluids and sodium. Adjust before your next match.

OffCourt tip

Save a two-minute heat check template in OffCourt. Tap HR seated, HR standing, delta, perceived clarity, and planned action each changeover. The app’s simple tags keep you honest under stress.

The Cooling Ladder: what to do and when

Cooling works when you time it. Here is a ladder you can run from light to strong based on how you feel. You do not need special gear beyond a cooler, ice, water, towels, and a squeeze bottle.

Level 1: Between points (5 to 10 seconds)

• 3–6–9 breathing: Inhale through the nose for 3. Exhale for 6. Three cycles. It drops heart rate and steadies the toss.
• Gaze anchor: Pick a single spot on your strings for two seconds. This clears visual noise.
• Hand splash: Squeeze a small stream of cold water over your hands and wrists before you start your serve routine.

Cues

• Think quiet chest. Loose jaw. Soft shoulders.
• Decide your next target before you walk to the line.

Level 2: Changeovers (60 to 90 seconds)

• Neck ice towel: Wring a cold towel around a handful of ice. Drape over the back of your neck for 30 to 45 seconds. Rotate the towel halfway.
• Forearm cooling lite: Press the towel along both forearms for 10 to 15 seconds each. This cools where blood flows close to the skin.
• Cold water to tongue and cheeks: Small sips of cold fluid, swish for 5 seconds. Swallow. Cold in the mouth cools the brain more than warm fluid.
• Clothing vent: Open your collar. Swap a soaked hat or wristbands if possible.

Fluids at changeover

• 150 to 250 ml per changeover if sweat rate is moderate.
• Up to 300 ml if high sweat rate and stomach feels settled.
• Add sodium if you see salt marks or cramp history.

Level 3: Set breaks or extended pauses

• Forearm immersion: Place forearms in your cooler for 30 to 60 seconds if you can. Water at 10 to 15 C works best. If that is not possible, keep rotating the ice towel on neck and forearms for the full break.
• Ice slush: 200 to 300 ml of ice slurry before the next set if you tolerate it. Slush cools core faster than cold water.
• Shirt swap: Change into a dry top if rules and time allow.

Level 4: Emergency cues

Stop and seek medical help if you feel dizzy, chills, confusion, or if cramps spread rapidly. No match is worth a hospital visit.

OffCourt cue card

Create a Cooling Ladder card in your bag. Level 1 to Level 4. Short, bold lines. You will use it when brain fog hits.

Pacing that wins in heat

Hot days reward clear, repeatable decisions. Here is how to keep the serve clock on your side and your shots high value.

Between points routine that fits 12 to 20 seconds

• Walk to the towel. One wipe. 3–6–9 breathing while you walk.
• Strings and gaze anchor for two seconds.
• Name the target and first step. Serve T, backhand to the open court. Or deep middle return, recover to baseline hash.
• Bounce count trimmed to your minimum consistent number. Consistency beats ritual length.

Tactical cues

• Deep to big targets. Middle wins in heat. Aim deep middle more often to reduce running and force errors.
• Serve body to start games. Body serve reduces opponent angles and your movement.
• Buy rest with height. Add one meter over the net on neutral balls.
• Cut patterns, not effort. Pick two serve-plus-one patterns and live there.

I used the 3–6–9 routine running a half marathon in August. Same effect on court. Heart rate settled and thoughts cleared in under ten seconds.

DIY sweat rate and sodium calculator

You cannot copy a pro’s drink plan. You need your numbers. Do this test in similar heat to your next event.

Sweat rate test

What you need: scale, bottle with volume marks, towel, watch.

• Pre-session: Void bladder. Towel off. Weigh yourself with dry clothes or minimal kit.
• Train 60 minutes at match pace. Record exactly how much you drink during the session.
• Post-session: Towel off sweat. Weigh again in the same clothing.

Formula

• Sweat rate L per hour = (pre weight kg − post weight kg) + fluid intake L − urine L.
• Most players will not pee mid-test. If you do, estimate volume and subtract it.

Example

• Pre 72.0 kg. Post 70.9 kg. Drank 0.6 L. No urine. Sweat rate = (1.1) + 0.6 = 1.7 L per hour.

Sodium replacement

You will not know your sweat sodium from a lab at most events. Use this field guide.

• Light salter: no visible salt marks. 500 to 700 mg sodium per liter of sweat.
• Moderate: faint salt rings on hat or shirt. 800 to 1000 mg per liter.
• Heavy: crusty white marks. Stinging eyes. 1100 to 1400 mg per liter.

Calculation

• Sodium per hour = sweat rate L per hour × target mg per liter.
• Using the example above and a moderate sweater at 900 mg per liter: 1.7 × 900 = 1530 mg sodium per hour.

How to hit that number

• Many sports drinks give 300 to 600 mg per liter. You may need to add electrolyte capsules or packets. Split across changeovers and set breaks.
• Start earlier. 300 to 500 ml fluid 2 hours pre-match. 200 ml 15 minutes pre-match. Include some sodium if you are a heavy sweater.

Stomach check

• Good signs: no slosh, normal burping, steady energy.
• Bad signs: slosh, cramps, bloat. Reduce volume per changeover and raise sodium concentration slightly. Spread sips across two changeovers.

OffCourt planner

Log sweat rate and sodium target once. OffCourt will auto-calc per-hour and per-changeover targets for match length. Print or save a simple card with numbers.

On-court heat drills that build skill and resilience

These are tennis-first. They layer cooling and pacing into point play. Use a timer.

Drill 1: Serve clock pressure with breath resets

• Setup: One server, one returner. 3 balls in pocket. Serve clock set to 20 seconds for practice.
• Work: 4 sets of 8 serves. Alternate deuce and ad. After each serve, run the 3–6–9 breath and one gaze anchor before the next toss.
• Scoring: 1 point for a made serve to target. Bonus point for holding toss time under 18 seconds.
• Rest: 60 seconds between sets. Use neck towel for 30 seconds.
• Cues: Quiet chest on exhale. Decide target before you pick up the ball.

Drill 2: Middle first in heat

• Setup: Baseline rally to deep middle targets only.
• Work: 3 blocks of 6 minutes continuous rally at 70 to 80 percent effort.
• Mod: Every second minute, both players add one meter net clearance and take one step back to buy time.
• Rest: 2 minutes between blocks. Neck towel 45 seconds. 150 to 250 ml fluid.
• Cues: Heavy, high, middle. Feet quiet between shots.

Drill 3: Heat ladder points

• Setup: Play points to 15, 30, 40, game. Escalate cooling each step.
• Work: 4 games per set. Set 1 Level 1 cooling only. Set 2 Level 2 on changeovers. Set 3 Level 3 on the set break.
• Rest: 90 seconds at changeovers. 2 minutes at set breaks.
• Cues: One pattern per game. Serve body to start each game.

Drill 4: Forearm cool and go

• Setup: Cooler courtside. Towels ready.
• Work: 5 rounds. Each round is 5 minutes of high-pace cross-court live ball, then 45 seconds of forearm cooling and neck towel.
• Rest: 75 seconds between rounds. Sip 100 to 150 ml fluid.
• Cues: Keep height when you feel rushed. Step back a half step rather than swing harder.

Simple heat readiness test

Run this one week before your target event in similar heat.

• Block A: 12 minutes of live baseline at 70 percent. Track average rally length and unforced errors.
• Changeover: Two-minute heat check. Record orthostatic HR delta.
• Block B: 12 minutes at 80 percent with serve plus one patterns.
• Data to pass:
  • Orthostatic HR delta 15 bpm or less at both changeovers.
  • Body mass loss 2 percent or less over 30 minutes of total work.
  • Unforced errors not rising more than 20 percent from Block A to B.
  • Perceived clarity 7 out of 10 or higher.

If you fail one metric, adjust cooling and sodium. If you fail two or more, reduce pace, increase pre-cooling, and retest in 48 hours.

OffCourt tracking

Use the Heat Readiness template. It logs HR deltas, body mass, RPE, and error count in one card. Simple traffic light output.

Two-week microcycle to prep for late-summer events

This plan assumes you play matches on the second weekend. Shift days to match your schedule. Aim for similar time-of-day heat exposure as your event.

Week 1: Build tolerance and routines

• Day 1 Mon: Skill + heat exposure

  • 75 minutes total. 45 minutes hitting with Drill 2. 3 sets of Drill 1. Level 1 and 2 cooling.
  • Fluids: target 70 percent of your tested sweat rate.
  • Strength: 20 minutes core and hips.

• Day 2 Tue: Match play light

  • 60 to 75 minutes set play to 4 with Level 2 cooling.
  • Run the two-minute heat check each changeover.

• Day 3 Wed: Off or active recovery

  • 30 minutes easy bike or walk in shade. Mobility 20 minutes. Hydration focus.

• Day 4 Thu: Heat ladder focus

  • 90 minutes. Drill 3 and Drill 4. Practice Level 3 cooling at a set break.
  • Fluids: target 80 to 90 percent of sweat rate. Add sodium to match your target.

• Day 5 Fri: Serve patterns + breath

  • 60 minutes focused on Drill 1 and first-ball patterns.
  • Finish with 10 minutes of shadow swings in shade using 3–6–9 breathing.

• Day 6 Sat: Practice match

  • Best of three short sets. Full Cooling Ladder. Track HR deltas.

• Day 7 Sun: Rest

  • Gentle mobility. 2 liters of fluid across the day with sodium to hunger and thirst.

Week 2: Specificity and taper

• Day 8 Mon: Heat readiness test

  • Run the full Simple heat readiness test.
  • Adjust plan based on results.

• Day 9 Tue: Pattern polish

  • 60 minutes. Serve plus one. Return plus one. Level 1 cooling between points. Level 2 on changeovers.

• Day 10 Wed: Short, hot, sharp

  • 50 minutes mid-afternoon. Two blocks of Drill 2 and 10 minutes of point play to 30. Hit pre-cooling with ice slush.

• Day 11 Thu: Light

  • 40 minutes easy hit. Stretch. Early night.

• Day 12 Fri: Pre-match primer

  • 45 minutes. Warmup, serves, first-ball patterns. One set of Drill 1. Test your Cooling Ladder gear.

• Day 13 Sat: Match

  • Execute your fluid and sodium plan. Cooling Ladder in play. Log changeover notes.

• Day 14 Sun: Recovery

  • 20 to 30 minutes very easy. Post-match cooldown below. Debrief in OffCourt.

Post-match cooldown that actually helps performance tomorrow

• Minute 0 to 2: Walk and breathe. 3–6–9 for three cycles. Do not sit yet.
• Minute 2 to 6: Neck towel on and rotate every 45 seconds. Gentle forearm cooling.
• Minute 6 to 10: 300 to 500 ml fluid with sodium. If appetite is low, use a slush.
• Minute 10 to 15: Legs up on a bench for 3 minutes. Light calf pumps. Then walk and stretch hips.
• Food within 45 minutes: carbs and protein. Salt to taste if you are a heavy sweater.

Gear checklist for hot matches

• Two towels. One stays dry for grip. One is your ice towel.
• Cooler with ice and water. Bottles with volume marks.
• Extra hat and wristbands. Dry shirt for set breaks if allowed.
• Small scale for pre and post weigh-in in the locker room.
• OffCourt heat cards printed or on your phone.

Troubleshooting

• I cramp at 4–4 in the second set

  • Raise sodium to the next bracket. Start earlier in the match. Add forearm cooling at every changeover. Serve body to reduce chase.

• My stomach sloshes when I drink more

  • Reduce volume per changeover and raise sodium concentration. Use colder fluid. Sip earlier in the set instead of late.

• I lose mental clarity late

  • Commit to one pattern per game. Shorten your routine. Always run 3–6–9 after long points.

• My serve toss wanders in the heat

  • Gaze anchor on the strings. Exhale before the toss. Use the same minimum bounce count every time.

Quick reference: numbers to remember

• Orthostatic HR delta: 0 to 15 bpm green. 16 to 25 yellow. More than 25 red.
• Body mass loss: keep it under 2 percent.
• Fluids: 150 to 300 ml per changeover depending on your sweat rate and stomach.
• Sodium: 500 to 1400 mg per liter of sweat depending on saltiness.
• Breath: 3–6–9 for three cycles = about 30 to 40 seconds of reset.

Summary

Heat will punish poor pacing more than poor fitness. New York showed that longer rallies and hotter surfaces are not going away. Your edge is a tight loop: check fast, cool fast, pace simple. Pair that with a sweat and sodium plan you tested. Then track it with something you will actually use.

On-court next steps

• Run the sweat rate test this week in similar heat.
• Build your Cooling Ladder kit. Practice it in two sessions.
• Add the two-minute heat check to every changeover in practice sets.
• Program two serve-plus-one patterns and train them under a 20-second serve clock.
• Log your first heat readiness test in OffCourt and adjust.

Final checklist

• Cooling Ladder card in bag
• Two towels, extra hat, wristbands
• Cooler, ice, marked bottles
• Pre and post-match weigh-in plan
• Sodium plan per hour and per changeover
• Serve routine with 3–6–9 breathing
• OffCourt tracking templates ready