Weather Radar
A beginner-friendly guide to radar imagery, precipitation echoes and the limits of radar information.
What weather radar does
Weather radar sends electromagnetic pulses into the atmosphere and measures energy scattered back by targets such as raindrops, snow and hail. Processing these returns helps estimate where precipitation is located and how it is moving.
Colors are not universal
Radar maps often use colors for estimated precipitation intensity, but the scale is not identical across services. Always read the legend for the radar product you are viewing.
Radar is not a simple rain camera
Radar estimates can be affected by distance, terrain, beam height, attenuation and non-weather echoes. Very light precipitation can be missed, and some reflections may not represent rain. Radar shows precipitation in the atmosphere, which does not always equal what reaches the ground.
Movement matters
A single radar frame is a snapshot. Several frames in sequence can show whether a precipitation area is moving toward or away from a location. Short-term movement can change quickly, especially with thunderstorms.
When to use official alerts
Radar is useful for visualizing precipitation but is not a replacement for official severe-weather warnings. If an authority issues an alert, follow that guidance.
Worked example: checking apparent approach speed
In an imaginary radar animation, a rain band is 30 km west of a town at 14:00 and 20 km west at 14:20. Its apparent approach speed is 10 km in one-third of an hour, or 30 km/h. Continuing that motion would put it near the town around 15:00.
That is a simple extrapolation, not a forecast promise. The band may weaken, grow, change direction or miss the town. Check the age of the newest frame before using the estimate: a delayed image moves the starting point of the calculation into the past.
Is the dashboard a radar image?
The site's temperature, cloud and precipitation values are numerical model output. A weather icon or cloud percentage is not a radar scan. When using an external radar map, confirm its coverage, observation time, legend and whether the animation includes predicted future frames.
Can I identify lightning from rain colors?
No. A precipitation color scale does not locate every lightning strike or determine storm safety. Use official warnings and lightning information where available; do not wait for a strong-colored echo over your position before acting on a warning.
Radar reference
The NWS radar interpretation reference explains sampling and radar products. For missing or misleading echoes, read what radar can miss; for storm hazards, read thunderstorm basics.
Editorial note: Weather information varies by location, observation source and update time. This article is for general education and everyday planning. For severe weather or safety-critical decisions, follow the relevant official meteorological and emergency authorities.