Answers first. Explanations after.
Most of these questions get asked with shoes already on. Every page here leads with the decision, names the authority behind it, and says what would make you stop.
Thresholds on these pages come from the US National Weather Service, the EPA and other public authorities — not from running convention. Where an authority gives guidance but no number, we give the guidance and no number.
Can I run today?
Enter what it is doing outside. The worst signal decides — good air quality does not make dangerous heat acceptable.
For particle pollution EPA counts people with heart disease, people with lung disease including asthma and COPD, older adults, children and teenagers, pregnant people, minority populations and outdoor workers. Ticking the box applies EPA’s sensitive-group guidance rather than its general guidance. It is not medical advice.
Not today — move it indoors or to another time
- Do not runDanger110°F heat index in full sun
Heat cramps and heat exhaustion are likely, and heat stroke is possible, with prolonged exposure or strenuous activity.
US National Weather Service
Our suggestion Move the run indoors or to another day.
- GoGoodAQI 45
A great day to be active outside.
US EPA / AirNow
Heat and air quality today. Storms and daylight are the next signals to join this check. Enter conditions from your weather app or AirNow.