The temperature on your weather app is built for someone standing at a bus stop. It is not built for you, halfway into a tempo run, generating heat with every stride. That gap is the single biggest reason runners get dressed wrong: they read the number, dress for the number, and spend the first mile freezing or the last mile cooking.
RunFeel is our answer to that gap. It is a run-adjusted temperature: a single number that estimates how the conditions will actually feel once you are moving, so the recommendation is built around your run instead of around a thermometer.
Running makes its own heat
The starting point is simple physiology. The moment you start running, your muscles turn fuel into motion, and most of that energy comes out as heat. Your body sheds it by pushing blood to the skin and sweating, which is why you warm up within minutes and why the layer that felt right at the door feels like too much by the end of the block.
Coaches have taught a version of this for decades with the "dress 10 to 20 degrees warmer" rule: add roughly that much to the air temperature before you decide what to wear, because exercise turns your body into a heat engine. RunFeel does that math precisely instead of by gut feel.
What RunFeel adjusts for
RunFeel starts with the feels-like temperature from the weather data, which already folds in wind chill and humidity, so it is closer to lived experience than the raw air temperature. Then it adds warming shifts based on how you actually run:
- Your profile. Some people run hot, some run cold. That changes the baseline.
- Your pace. A hard effort generates far more heat than an easy jog.
- Your distance. The longer you are out, the more heat builds up.
The shifts stack but are capped, so an extreme combination never runs away into nonsense. If you want the exact figures and the research behind them, the full breakdown lives on the how it works page.
Why two runners need different kit at the same temperature
This is the part a plain forecast can never capture. On a 40-degree morning, a fast runner heading out for 10 miles will be warm within a mile and is fine in a long sleeve over shorts. Someone doing an easy two-mile jog at the same 40 degrees stays cooler the whole way and wants an extra layer. Same air, different runs, different answers. RunFeel is what lets the recommendation tell them apart.
It works in the other direction too. A 60-degree run feels mild at an easy pace, but push the effort and RunFeel climbs into genuine warm-weather range, which is your cue to drop a layer and start thinking about sweat.
How to use it
The practical takeaway is the oldest rule in cold running: start slightly cool. If you feel a touch underdressed standing at the door, you have probably dressed for the run rather than the doorstep. RunFeel is just a way to make that instinct reliable, and to carry it across the harder calls, like dressing for the cold or reading the feels-like number when wind and humidity pull it away from the thermometer.