Running in Hot Weather: Essential Tips to Prevent Heat Exhaustion and Stay Safe

Why Heat Makes Running Harder

Every 10°F increase in temperature raises your heart rate by 5-10 beats per minute at the same pace.

When it's hot, your body diverts blood to your skin for cooling, leaving less oxygen-rich blood for working muscles. The result? The same pace feels significantly harder.

Heat affects performance:

60-70°F: Ideal running temperature
70-80°F: Slight performance decrease (2-5%)
80-90°F: Moderate impact (5-10% slower)
90°F+: Significant impact (10-20% slower), heat illness risk

Bottom line: You'll need to slow down in hot weather—and that's completely normal.

When to Run in Summer

Best Times

Early morning (5-7am):

Coolest temperature of the day
Lower humidity (usually)
Sun angle less intense
Quieter roads

Evening (7-9pm):

Second-coolest option
Sun is setting (less direct exposure)
Note: Pavement still holds heat from day

Worst time: Midday (11am-3pm) when sun and temperature peak

Consider Indoor Running

When it's too hot outside:

Heat index over 95°F
High humidity (over 70%)
Air quality warnings
You're not heat-acclimated

Treadmill benefits:

Controlled temperature
Consistent pace
Safety
No sun exposure

No shame in moving inside when conditions are dangerous.

Pace Adjustments for Heat

The Pace-Temperature Formula

For every 5°F above 60°F, slow down by 10-20 seconds per mile.

Example: Your normal easy pace is 9:00/mile at 60°F

70°F: Run 9:10-9:20/mile
80°F: Run 9:20-9:40/mile
90°F: Run 9:40-10:00/mile
95°F+: Consider skipping or moving indoors

Run by Effort, Not Pace

Ditch your GPS watch (or ignore the pace)

Use these effort indicators:

Can you hold a conversation?
What's your breathing like?
How hard does it feel?

On hot days:

Easy runs should still feel easy (even if pace is slower)
Hard workouts may need to be adjusted or moved indoors
Long runs should be significantly slower

Heat Acclimation Takes Time

Your body needs 10-14 days to adapt to heat.

Adaptations that occur:

Increased sweat rate (better cooling)
Earlier onset of sweating
Reduced heart rate at given pace
Better fluid retention
Improved heat tolerance

How to acclimate safely:

Start with shorter runs (20-30 min)
Gradually increase duration
Run at easy effort only
Don't attempt hard workouts until week 2-3

If you live in a hot climate, you'll naturally acclimate. If traveling to heat, arrive early to adapt.

Hydration in the Heat

Drink More, Start Earlier

Hot weather hydration (see our full hydration guide):

Pre-run (2-4 hours before):

20-24 oz water (4-6 oz more than usual)
Include sodium (salty breakfast, electrolyte drink)

During run:

Under 30 min: Not necessary
30-60 min: 4-8 oz every 15 min
Over 60 min: 6-10 oz every 15 min with electrolytes

Post-run:

20-24 oz per pound lost
Continue sipping for 2-4 hours

Carry Water

For runs over 30 minutes in heat, bring fluids:

Handheld bottle
Hydration vest or belt
Plan route with water fountains
Stash bottles along route

Use Electrolytes

When it's hot, sweat more = lose more sodium.

Electrolyte sources:

Sports drinks (Gatorade, Nuun, Tailwind)
Salt tablets
Electrolyte gels
Salty snacks pre-run (pretzels, pickles)

Target: 300-600mg sodium per hour for runs over 60 minutes

Clothing and Gear for Hot Weather

What to Wear

Best fabrics:

Lightweight, moisture-wicking synthetic
Light colors (reflect heat)
Loose-fitting (allows air circulation)
Minimal coverage (singlet, short shorts)

Avoid:

Cotton (holds sweat, feels heavy)
Dark colors (absorb heat)
Tight compression gear (traps heat)

Critical Accessories

Hat or visor:

Keeps sun off face and scalp
Choose light-colored, breathable fabric
Visor allows heat to escape from head

Sunglasses:

Protect eyes from UV
Reduce squinting (and headaches)
Polarized lenses reduce glare

Sunscreen:

SPF 30+ water-resistant
Apply 15-30 min before running
Reapply if over 90 minutes

Cooling gear (optional):

Cooling towel around neck
Ice bandana
Cooling vest (for pre-run)

Cooling Strategies

Before Your Run

Pre-cooling reduces core temperature:

Cold shower or ice bath (5-10 min)
Drink cold fluids (16-20 oz)
Stay in air conditioning until last minute
Wet hair and bandana

During Your Run

Cool yourself continuously:

Pour water on head, neck, wrists
Run through sprinklers or water fountains
Wet your shirt at aid stations
Seek shaded routes (trails, tree-lined streets)

After Your Run

Recover faster:

Cold shower or ice bath
Cold fluids immediately
Move to air conditioning
Elevate legs

Warning Signs of Heat Illness

Heat Exhaustion (Serious)

Symptoms:

Heavy sweating
Weakness or fatigue
Dizziness
Nausea
Headache
Muscle cramps
Cool, clammy skin

Action:

Stop running immediately
Move to shade or air conditioning
Drink cool fluids with electrolytes
Cool body with wet towels
Rest and monitor symptoms

Heat Stroke (Life-Threatening Emergency)

Symptoms:

High body temperature (103°F+)
Confusion or altered mental state
Cessation of sweating (skin dry and hot)
Rapid pulse
Nausea/vomiting
Loss of consciousness

Action:

Call 911 immediately
Move to shade/AC
Cool body with any means possible (ice, cold water)
Do not give fluids if unconscious

Never ignore these symptoms. Heat stroke can be fatal.

When to Skip the Run

It's Too Hot to Run If...

✗ Heat index over 100°F ✗ Air quality index "unhealthy" or worse ✗ You're feeling dizzy, nauseous, or weak before starting ✗ You're recovering from illness ✗ You haven't been sleeping well ✗ You're dehydrated (dark urine, persistent thirst)

Running in extreme heat doesn't make you tougher—it makes you injured or sick.

Better options:

Move workout indoors (treadmill, gym)
Swim or aqua jog
Bike in air conditioning
Cross-train
Rest day

Missing one workout is better than heat illness sidelining you for weeks.

Workout Adjustments for Hot Weather

Easy Runs

Slow pace by 20-60 seconds per mile
Shorten distance by 10-20%
Run by effort (ignore pace)

Long Runs

Start extra early (before sunrise)
Plan route with shade and water access
Slow significantly (30-90 sec/mile slower)
Consider breaking into two shorter runs

Speed Workouts

Option 1: Move to treadmill (air conditioned) Option 2: Run early morning only Option 3: Reduce volume (fewer reps, shorter intervals)

Example:

Normal: 8 × 800m
Hot weather: 5 × 800m or move indoors

Races in the Heat

Start conservatively (slower than goal pace)
Pour water on body at every aid station
Use electrolytes throughout
Adjust goals (time goals become effort-based)

Personal records are unlikely in hot races—focus on finishing strong and healthy.

Building a Heat-Safe Summer Training Plan

Week-by-Week Approach

Weeks 1-2: Acclimation

Reduce mileage 20-30%
All runs at easy effort
Focus on consistency

Weeks 3-4: Gradual Build

Return to normal mileage
Add back one quality workout (adjust pace/volume)
Monitor recovery carefully

Weeks 5+: Normal Training (with heat adjustments)

Full training load
Run by effort, not pace
Strategic use of indoor training

Stay Flexible

Hot weather requires adaptation:

Move runs to cooler times
Swap outdoor for indoor sessions
Take extra rest if needed
Don't force workouts in unsafe conditions

Training plans should bend, not break.

How kovaa Handles Hot Weather Training

Smart coaching adapts to conditions.

kovaa automatically adjusts:

Weather-based pace recommendations: Slower targets when it's hot
Hydration reminders: Alerts for runs requiring fluids
Workout rescheduling: Suggests moving hard sessions to cooler days
Recovery monitoring: Increases recovery time after hot-weather runs
Safety alerts: Warns when conditions are dangerous

The result: You train effectively without overheating or underperforming.

Summer Running Checklist

Before running:

Check temperature and heat index
Run early morning or late evening
Pre-hydrate (20-24 oz, 2-4 hours before)
Apply sunscreen (SPF 30+)
Wear light-colored, moisture-wicking clothes

During running:

Slow pace by 20-60 seconds per mile
Carry water for runs over 30 min
Use electrolytes for runs over 60 min
Seek shade when possible
Pour water on body for cooling

After running:

Rehydrate immediately (20-24 oz per pound lost)
Cool down (cold shower, AC)
Monitor for heat illness symptoms
Rest and recover fully

Final Thoughts

Summer running is about smart adaptation, not toughness.

The runners who thrive in heat:

Adjust pace based on conditions
Run at cooler times of day
Prioritize hydration and electrolytes
Listen to their body
Move workouts indoors when necessary

The runners who struggle or get injured:

Force the same pace regardless of temperature
Run at midday in peak heat
Ignore hydration needs
Push through warning signs

Your body can't defy physics—heat slows you down. Accept it, adjust for it, and train smart.

Ready for weather-adaptive training that keeps you safe and progressing? Download kovaa today.