How do you stay safe ultrarunning in the heat?
Hot ultras and long training runs need a cooling plan, not just a hydration plan: acclimatize gradually in the weeks before, start slower than you want to, use ice and water on your skin at every aid point, and take in electrolytes and food. Drop or rest at the first sign of heat illness. Alone in training, set a return time so Holler alerts your Guardians if you do not finish when expected.
Heat plan for long days
01Acclimatize before the race
Build hot-weather miles gradually over the weeks before a warm event. Your body adapts by sweating earlier and holding onto salt better. Arriving from a cool climate to run a hot 50 miler without preparation is a big risk.
02Start slow and stay there
In a long race, heat compounds over hours. Holding back in the first quarter pays off late in the day. Walk the climbs and in the hottest stretches, and adjust your goal time to the forecast.
03Cool from the outside
Stuff ice in a buff or hat, sponge water over your head and arms, and soak your shirt at every aid station or creek. External cooling is one of the most useful tools in a hot ultra.
04Balance fluid, salt and food
Drinking only plain water for many hours without food or electrolytes can cause its own dangerous problems. Follow a plan you have tested in training, and talk to a doctor or sports dietitian if you have had trouble before.
05Know when to stop
The CDC lists headache, nausea, dizziness, weakness and heavy sweating as signs of heat exhaustion. Confusion, slurred speech, seizures or collapse point to heat stroke: the National Weather Service says call 911, cool the runner with water and wet cloths, and do not give fluids. At a race, tell aid station or medical staff the moment you feel off. Dropping is a good decision, not a failure.
06Protect solo training runs
Long training runs alone in the heat are where no aid crew is watching. Holler cannot sense heat illness, so set a return time: miss it by five minutes and your Guardians get an overdue alert with your last location. A stationary alert can flag a long stop too.
Related questions
Does my crew need to watch for heat illness?
Yes. Brief your crew and pacer on the signs, especially confusion, which you may not notice in yourself. A pacer who knows you well will spot a change in speech or mood.
How can my crew follow me between aid stations?
A live location link lets your crew see your position in any browser without an app, so they can time aid station arrivals. Our page for ultrarunners covers crew setups and phone battery.
Should I train at night to avoid the heat?
It trades one risk for another. Night miles are cooler but darker, with trips, wildlife and fewer people around. Carry a main light and a backup, stick to trails you know, and keep your live link on so a Guardian can see the route travelled. Our headlamp guide covers brightness and battery for long nights.
Is it OK to push on through nausea?
Nausea is common in long races, but in the heat it can be an early sign of heat exhaustion. Slow down, cool off in shade, and reassess. If it comes with confusion or dizziness, stop. More in the heat safety guide.
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Sources, checked September 2026: CDC NIOSH: Heat-related illnesses, CDC: People at higher risk from heat, National Weather Service: Heat exhaustion and heat stroke.
More safety answers, or see the safety guides.