Too hot
Should I run when it's hot?
Too hot
"The sun isn't a reason to stop, it's just a running companion. Go."
Now what?
- ·Whatever you wore last time still works.
- ·25-30 minutes at conversational pace. Nothing to prove.
Or, what's your excuse?
Get a fresh roast every morning at 6 AM your time.
One short email. Skip it any day you don't need it.
Heat is the one condition on this list where the honest answer includes a real limit. Cold you can dress for and rain you can ignore, but heat has to be managed, and the runners who get into trouble are almost always the ones who ran their normal session at their normal pace on a day that was not normal.
Humidity matters as much as temperature, because sweat only cools you when it evaporates. At 30C and dry you can work with it. At 28C and very humid your main cooling system is running at half efficiency, and your heart rate at easy pace will tell you so within ten minutes.
Adaptation is real but slow — roughly ten days to two weeks of consistent exposure before the same heat feels manageable. Until then, and on the worst days regardless, the answer is earlier, shorter and slower. That is not backing down. Running the planned session in a heat warning is not toughness, it is just a bad read of the conditions.
- Go early. Dawn is often ten degrees cooler than the same run at 6pm.
- Humidity matters as much as heat. Sweat that cannot evaporate cannot cool you.
- Drop the pace target before you leave. Same effort, slower splits, no argument.
- Heat adaptation takes 10-14 days. The first hot week is meant to feel awful.
- Drink to thirst and add electrolytes on anything over an hour in real heat.
- Shade and loops beat a scenic point-to-point. Plan for water on the route.
- Light, loose, pale clothing and a cap. Sunscreen on everything still exposed.
- Stop if you go cold, clammy, dizzy or stop sweating. That one is not negotiable.
FAQ
Is it too hot to run?
It depends on humidity as much as temperature, and on how heat-adapted you are. As a rule, above roughly 30C — or lower with high humidity — shift to early morning, shorten the run and drop the pace. During official heat warnings, move the session indoors.
What is the best time to run in summer?
Early morning, before sunrise if you can manage it. Air temperature, road surface temperature and UV are all at their lowest, and humidity is less punishing than the same figure later in the day. Evening is the second-best option but the ground still radiates stored heat.
How much slower should I run in the heat?
Significantly, and the hotter and more humid it is the bigger the gap. Run by effort or heart rate rather than pace, accept splits that would look bad in spring, and understand that you are not losing fitness — you are paying a cooling tax.
How do I run in humidity?
Accept a slower pace, run shorter, wear as little as decency and sunburn allow, and choose loops that pass water. Humidity blocks evaporative cooling, so your usual pace at your usual effort is simply not available that day.
What should I drink when running in the heat?
Water for anything under an hour, and something with electrolytes beyond that or when you are sweating heavily. Drink to thirst rather than forcing large volumes, and start the run already hydrated instead of catching up during it.
What are the warning signs of heat illness when running?
Dizziness, nausea, headache, confusion, clammy or unusually cold skin, and stopping sweating despite the heat. Stop immediately, get into shade, cool down and get fluids — and seek medical help if symptoms include confusion or you do not improve quickly.
How long does it take to get used to running in heat?
Roughly ten days to two weeks of consistent exposure produces meaningful adaptation, with plasma volume and sweat response both improving. The first hot week of the year always feels disproportionately hard, and that is expected rather than a fitness problem.
Should I use a treadmill when it is too hot?
During heat warnings or extreme humidity, yes — that is exactly what it is for. On merely warm days, going earlier and slower generally beats going indoors, since you also lose the heat adaptation you are trying to build.