Temperature, wind, humidity and rain — what you actually need to know before you head out the door, and an instant forecast for wherever you are.
Check today's running weather →Temperature is the single most important factor in running performance. Running generates a significant amount of body heat — roughly 75–80% of energy used in running becomes heat rather than forward motion. That heat has to go somewhere.
Temperature alone does not tell the whole story. Humidity has a massive effect on how hard running feels, because it limits the body's ability to cool through sweating. At 28°C and 30% humidity, running feels challenging. At 28°C and 80% humidity, it can feel unbearable and genuinely dangerous for longer distances. The "feels like" temperature shown by WeatherForIt accounts for both.
Below 5°C, some runners experience airway tightening, especially those with exercise-induced asthma. Breathing through a snood or neck gaiter can warm the air before it reaches your lungs. Cold air itself is not dangerous to breathe for most healthy people, but the sudden transition from cold to warm on finishing your run can trigger a coughing fit — allow yourself to cool down gradually.
If temperatures have jumped suddenly (a heat wave following a cool spring), your body needs 7–14 days to acclimatise. During this period, perceived effort at the same pace will be significantly higher. Reduce your training load by 20–30% and prioritise running in the cooler parts of the day.
Wind affects runners differently than cyclists — at typical running speeds of 8–14 km/h, you create some wind resistance yourself. A strong headwind adds measurable effort; a tailwind helps less than it feels like it should.
| Wind speed | Gusts up to | Verdict | What to expect |
|---|---|---|---|
| 0–10 mph | 14 mph | Very Doable | Barely noticeable. No pace adjustment needed. Ideal running conditions. |
| 11–20 mph | 28 mph | Very Doable | Noticeable headwind. Running into it adds effort; use it as part of the session. Plan an out-and-back with wind at your back on the return. |
| 21–28 mph | 38 mph | Take Care | Challenging into the wind. Gusts can push you off balance, especially on trails. Adjust pace expectations and avoid exposed ridge routes. |
| 29–38 mph | 50 mph | Best Avoided | Very difficult and potentially dangerous. Risk of being pushed into roads or off-path. Debris may be airborne. Treadmill is the better option. |
| 39+ mph | 60+ mph | Best Avoided | Storm-force conditions. Do not run outside. Trees and branches pose a serious danger. |
Research suggests a headwind of 10 mph adds roughly 12–20 seconds per mile compared to calm conditions. A tailwind of the same speed only saves about 5–8 seconds per mile. This asymmetry means an out-and-back run in windy conditions always feels harder overall than a calm day at the same pace.
On an athletics track, crosswinds affect the two straight sections differently and are felt almost as a headwind when you are running at 90 degrees to the direction of travel. Times on windy days are worth contextualising; a 20 mph crosswind can add several seconds per lap on a 400m track.
Many runners enjoy light rain — it keeps you cool and there is a certain satisfaction in running in conditions others avoid. But rain introduces specific risks worth knowing about.
This is perfectly runnable for most people. Wear a moisture-wicking top rather than cotton (which becomes heavy when wet). A light cap with a peak keeps rain off your face. Your feet will get wet unless you have trail shoes with some water resistance — accept it and focus on the run.
The main risks are chafing, hypothermia risk (if you get cold and wet), reduced grip on tarmac and trails, and reduced visibility — especially relevant if you are running on roads near traffic. Apply anti-chafe balm to armpits, inner thighs and any seam lines before long runs in rain. Have a dry warm layer waiting at the finish — getting out of wet kit quickly is essential.
Wet tarmac is generally fine. Wet painted lines (road crossings, kerb edges), wet metal (drain covers, gratings) and wet stone flags are as slippery as ice. On trails, wet clay becomes treacherous and trail shoes with proper lugs are essential. Fallen wet leaves in autumn are also a significant slip hazard on paths and pavements.
Wet fabric causes chafing far more quickly than dry fabric. On runs over an hour in rain, this becomes a real issue — particularly in the underarm area, inner thighs and across the chest for women. Anti-chafe sticks (e.g. Bodyglide or Vaseline) applied before the run prevent this entirely. Do not wait until you feel discomfort — by that point the damage is already done.
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