The short answer
Ordinary rain may call for waterproof clothing, slower travel, or a short delay. A thunderstorm adds lightning and may also bring gusty winds, poor visibility, rapid heavy rain, or hail. Those hazards can make walking, bicycling, boating, fishing, and open-air tours unsafe.
If you hear thunder or the sky looks threatening, NWS guidance is to enter a substantial building or hard-topped vehicle immediately. Wait at least 30 minutes after the last thunder before returning outside.
Rain location is not the lightning boundary
Lightning can threaten before rain begins at your exact location and after the heaviest rain has moved away. Do not use a dry sidewalk, light rainfall, or a radar gap as proof that an outdoor location is safe when thunder is audible.
Activities have different exposure
- Walking near buildings: shelter may be accessible, but trees, awnings, and open porches are not equivalent to a substantial building.
- Bicycling: the route may leave safe shelter several minutes away.
- Fishing or boating: water exposure and distance from substantial shelter require earlier decisions.
- Vehicle tours: the vehicle may provide shelter, but boarding, stops, and flooded roads still matter.
Organized storms change the scale
A line or complex of storms can create broader impacts and stronger wind than a single brief cell. Watches and warnings, forecast discussions, and operator decisions provide context that a simple rain icon cannot.
Practical takeaway
Ask whether the forecast contains rain or thunderstorms. If thunder is possible, know the shelter before starting and leave enough time to reach it. Do not wait for the first downpour to make the lightning decision.
Continue deciding
Sources and fact review
Meteorological guidance and public information were reviewed on . Forecasts and alerts change, so check current official information before relying on it.