How do you stay safe running in the heat?
Run early or late when it is coolest, slow your pace, drink before you are thirsty, and pick shaded loops that pass water fountains or stores. Learn the signs of heat exhaustion and heat stroke and stop at the first ones. Heat illness can leave you too confused to call for help, so set a return time before you go. If you are late, Holler alerts your Guardians.
A hot-weather running plan
01Move the run to the coolest hours
Early morning is usually the best window, before the pavement soaks up the sun. Evening can work, but roads and sidewalks stay hot after sunset. Check the heat index, not just the air temperature, since humidity makes it much harder for sweat to cool you. The National Weather Service notes that full sun can add up to 15°F to the heat index, so a shaded loop really does run cooler than an open one.
02Slow down on purpose
The same effort costs more in the heat, so run by feel or heart rate and let the pace drop. Hot days are for easy miles, not intervals or race-pace tests. If you are not used to the heat yet, keep the first few hot runs short and build up gradually rather than jumping straight to your usual long run.
03Plan water into the route
Short loops past your house, a park fountain or a store let you drink without carrying much. On longer runs, carry a handheld bottle. Wear light-colored, loose clothing and a cap or visor.
04Know when to stop
The CDC lists heavy sweating, headache, dizziness, nausea, weakness and thirst as signs of heat exhaustion, and the National Weather Service adds cool, pale, clammy skin and a fast, weak pulse. Stop, get into shade, loosen clothing and sip cool water; get medical help if you vomit, feel worse, or it lasts more than an hour. Confusion, slurred speech, hot skin or collapse point to heat stroke: call 911, cool the person with wet cloths or cool water, and do not give them fluids.
05Set a return time before you head out
Someone with heat stroke may not be able to use a phone, and Holler cannot sense heat illness. What it can do is watch the clock. Set a return time, and if you have not checked in five minutes after it, Holler sends your Guardians an overdue alert with your location, even if the app is closed.
06Share your route
A live location link lets a Guardian see where you stopped if something goes wrong. Pair it with a short route near home on the hottest days so help is close.
Related questions
How hot is too hot to run outside?
There is no single number, because humidity, sun, your fitness and how used to heat you are all matter. When the heat index is high, move indoors, cut the run short, or run at dawn. The CDC's HeatRisk forecast is a useful daily check.
Should I drink water or sports drink?
For most easy runs under an hour, water is fine. On longer or sweatier runs, something with electrolytes helps replace salt. If you have a medical condition or take medication that affects fluids, talk to your doctor about what is right for you.
Can Holler tell if I am overheating?
No. Holler cannot sense heat illness. A return time or a stationary alert is how it catches a run that went wrong: if you stop moving for too long or miss your check-in, your Guardians hear about it. Our heat safety guide for runners and hikers goes deeper.
Where should I keep my phone on a hot run?
In a pocket or waist belt, out of direct sun, and never left on a sunny bench while you do laps. Apple says iPhones work best between 32 and 95°F (0 to 35°C); an overheated phone can dim its screen, weaken its cellular signal and stop charging, which also slows the updates your Guardians see on your live link.
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Sources, checked September 2026: CDC NIOSH: Heat-related illnesses, CDC: About heat and your health, National Weather Service: Heat exhaustion and heat stroke, National Weather Service: Heat index and heat forecast tools, Apple Support: Keeping iPhone within acceptable operating temperatures.
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