How to Read Weather Radar: Colors, dBZ and Storm Shapes
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Weather radar sends out pulses of microwave energy and listens for the echo that bounces back off raindrops, snowflakes and hail. In the U.S., the National Weather Service runs a network of about 160 high-resolution Doppler radars called NEXRAD (WSR-88D), operated jointly by NOAA's National Weather Service, the FAA and the U.S. Air Force.
What the colors mean
Most radar maps show reflectivity, measured in dBZ (decibels of Z). The more energy that comes back, the higher the dBZ and the heavier the precipitation is likely to be.
| Reflectivity | Usual color | What it often means |
|---|---|---|
| Below ~20 dBZ | Light blue / light green | Very light rain, drizzle, light snow, or non-weather echoes |
| 20–40 dBZ | Green to yellow | Light to moderate rain |
| 40–50 dBZ | Yellow to orange | Heavy rain; thunderstorms |
| 50–65 dBZ | Red | Very heavy rain, possibly small hail |
| 65+ dBZ | Magenta / purple / white | Often hail |
Ranges are approximate; color scales differ between apps.
Shapes worth knowing
- Bow echo: a line of storms bulging outward like an archer's bow. It often brings damaging straight-line winds at the leading edge.
- Hook echo: a hook-shaped appendage on the back side of a supercell, which can indicate rotation and a possible tornado.
- Squall line: a long, narrow line of storms that can bring a burst of wind and heavy rain as it passes.
Velocity: seeing the wind
Doppler radar also measures how fast precipitation moves toward or away from the radar. On velocity maps, green usually means motion toward the radar and red means away. A tight pairing of bright green and bright red side by side, called a velocity couplet, can signal rotation.
Limits of radar
- The radar beam travels in a straight line while the Earth curves away below it, so far from the radar the beam is high above the ground and can miss low clouds and light precipitation.
- Mountains can block the beam.
- Birds, insects, dust and ground clutter can show up as echoes, especially near the radar site.
Related guides
Your World Weather Radar
The app's Radar plays rain past and ahead, keeps snow in light blue, and can add lightning and hurricane layers.
Sources
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- 💨 Wind, barometric pressure, moon and sun times, plus deer feeding times (Premium)
- 🗺️ Trip Planner with Ask Hawk and Top spots: public refuges and private lodges near you
- 🎧 Guides with a Listen button, in English and Spanish
Last reviewed November 2026. General information only; follow official guidance in an emergency.