How to Run an Ultra in the Heat Without Destroying Yourself

Heat kills more ultra dreams than any mountain. Your body can only cool itself so fast, and when ambient temperature exceeds 80°F, the math gets ugly fast.

Heat Acclimation

Start 10-14 days before your race. The protocol is simple:

• Run during the hottest part of the day (with appropriate safety precautions)
• Or add 20-30 minutes of sauna time after runs (160-180°F, seated)
• Your body adapts by increasing plasma volume, starting sweat earlier, and reducing core temperature rise

Research shows 10 days of heat acclimation improves performance by 7-10% in hot conditions. This is the single biggest thing you can do.

Race Day Strategy

Pre-cool: Drink an ice slurry 30 minutes before the start. Wear a cooling vest during warmup if available.

Pacing: Slow down 10-15% from your planned pace in temperatures above 75°F. For every 5°F above 75, add another 5% slowdown.

Hydration: Drink to thirst, but supplement with 500-700mg sodium per hour minimum. In extreme heat, you may need 1,000mg+.

Cooling opportunities: Ice in your hat, bandana, or vest at every aid station. Pour water on your head and wrists. Seek shade when possible.

Warning Signs

Heat exhaustion: Heavy sweating, weakness, nausea, dizziness, headache. Get to shade, drink fluids with electrolytes, pour water on yourself.

Heat stroke: Hot skin, confusion, loss of coordination, stopped sweating. This is a medical emergency. Stop running immediately and seek help.

The Best Hot-Weather Gear

• Light-colored, loose-fitting shirt (white reflects heat)
• Mesh-back hat with neck shade
• Handheld bottle for aid-station-to-aid-station cooling
• Light-colored shorts
• Sunscreen (reapply every 2 hours)

Know When to Quit

DNFing due to heat is not failure — it's intelligence. If you're experiencing confusion, vision changes, or uncontrollable vomiting, stop. There will be other races.