Radar observes; warnings communicate risk
Weather radar uses returned signals to help identify precipitation and its motion. An alert map displays messages issued by weather authorities for defined areas and time windows. These are complementary tools with different purposes. A warning can remain relevant even when rain at your location looks light.
Check the timestamp and legend
Before reading any radar display, inspect its time, units and legend. A still image cannot show whether a storm is approaching or moving away. Different products use different colors, and radar coverage or interpretation can be limited. Use the provider’s product guide to understand the specific layer.
What this site shows
Weather Alert Map can display U.S. composite radar from the Iowa Environmental Mesonet, based on National Weather Service radar, alongside official warning polygons where a provider supplies them. Radar colors describe precipitation returns. Severity colors describe warning classifications. They are not the same scale, and neither product is a street-level prediction. Follow the source link for the issuing service’s own radar and forecast products.
What the U.S. radar layer on this site is
The radar option uses composite reflectivity tiles from the Iowa Environmental Mesonet, built from National Weather Service radar. It shows where precipitation was detected, with a delay, for the United States. It is not a worldwide radar, not a rainfall total and not a forecast. Bright colors mean a stronger returned signal, which often corresponds to heavier precipitation, hail or other non-weather echoes. They are not the same scale as warning severity colors drawn on top of the map.
A quiet radar and a quiet warning map are different
No radar echoes means the composite did not show precipitation returns at that time in view. It does not mean a warning is cancelled, and it does not mean lightning is impossible. No warning polygon means this site did not have a current official message with geometry for that view. Coverage gaps, expired messages and feeds that failed all look quiet unless you read the status line. For a forecast of what happens next, use the hourly table and the issuing service’s own radar.
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.