Read more than the color
A warning combines several different questions: how serious could the impact be, how likely is the event, and how soon should you act? On this site, severity is displayed separately from the event name. A moderate label does not mean that every situation in the warning area is safe. Read the issuer’s description and instructions for the local details.
Why countries use different systems
National warning services use their own criteria, thresholds and terminology. Weather Alert Map preserves the issuing organization and original event name, while presenting Common Alerting Protocol severity labels in a consistent legend. These labels do not make two countries’ thresholds identical. Unknown means that a supported severity was not provided; it does not describe a low risk.
Check the warning window
Issued is the time a message was released. Effective indicates when its warning window begins, and expires marks its stated end. A message can be issued ahead of a hazard. Updates or cancellations may arrive before expiry, so check the official source when making a decision. A map with no displayed warning is not proof of safe conditions.
How to read a warning on this map
Open the warning and read four fields before you look at the color: the event name, the issuing office, the effective time and the expiry time. The color is a Common Alerting Protocol severity label. It does not, by itself, tell you whether a road is closed or whether you should evacuate. If the message lists counties, rivers or forecast zones, those names are the official area. A marker in the middle of a polygon is only a way to open the message.
What to do with an Unknown or Moderate label
Unknown means the source did not send a supported severity. It is not a statement that the weather is minor. Moderate and Minor still describe official messages. People outdoors, on the water, or in flood-prone places can be affected by a warning that looks less urgent on a legend. Compare the instructions in the message with a second official source, such as weather.gov for the United States, when you are making a safety decision.
Sources and further reading
Official National Weather Service reference. Source checked September 28, 2026. This general guide does not replace a current warning or advice from local authorities.
Check current warnings
Explore related live official warnings, or search your location for a forecast.