Running weather guides

Updated 2026-10-14 · Figures from the ArcPace weather model

How the weather changes a run: practical guides, and what drives your pace in the heat.

For a number: the running weather calculator gives a run score, pace cost and what to wear for any weather and your pace.

Running in the weather #

• How to run in the heat and stay cool
  Timing, pacing, cooling, drinking and two weeks to adapt.
• Heat illness warning signs: when to stop
  Cramps, exhaustion and heat stroke, and what to do for each.
• Running in the cold: what to watch for
  Layers, wind, ice, darkness, frostbite and hypothermia.
• Running in rain, wind, thunderstorms and smoke
  When to go anyway, when to go inside, and how to set up for each.
• Marathon race-day weather: how to read the forecast
  Start and finish hours, dew point, wind, sun, start-line layers and when to change your goal.

Pace, clothing and heat flags #

• How much do heat and humidity slow your running pace?
  What drives the slowdown, why dew point matters, and why slower runners lose more.
• What to wear running, by temperature
  From 10°F to 90°F, and how wind, rain and sun change it.
• WBGT and race heat flags, explained
  What wet bulb globe temperature measures, and what each race flag means.