Forecast periods
National Weather Service forecasts describe expected weather in future periods, including temperature, wind and precipitation information.
Reading weather forecasts — Guide
Guidance for U.S. Weather Forecast. Practical instructions, limitations, and accuracy tips.
This article explains the use and limitations of the interactive tool. No signup is required. Output can be approximate and should not substitute for authoritative sources when the stakes are high.
Rain probabilities
A probability of precipitation describes the likelihood of measurable rain at a point during the forecast period; it is not the percentage of time rain will fall.
Alerts and limitations
Use official National Weather Service alerts for urgent hazards. This site serves only NOAA-covered U.S. locations and requires a live network connection.