1. Check the time before the color
The newest frame may already be several minutes old because a radar must scan, process and transmit its data. Look for the observation time or a “live” marker. If the app shows future frames, identify the point where measurement ends and prediction begins.
2. Read the legend
Radar reflectivity describes how much transmitted energy returns to the radar. NOAA explains that the return depends on the size and amount of targets such as water droplets, ice crystals and sometimes insects. Reflectivity is usually expressed in dBZ.
Many consumer maps use cool colors for weaker returns and yellow, orange, red or purple for stronger returns, but palettes differ. Do not transfer a color meaning from one app to another without checking the legend.
| Typical dBZ range | Common interpretation | What to remember |
|---|---|---|
| Below 20 | Very weak echo or light precipitation | May not reach the ground |
| 20–35 | Light to moderate precipitation | Type depends on temperature profile |
| 35–50 | Moderate to heavy precipitation | Watch motion and local warnings |
| Above 50 | Very strong return | Can indicate intense rain, hail or mixed targets |
These bands are approximate, not a universal rain-rate conversion. Hail and melting snow can produce strong returns, and the same dBZ value does not always mean the same surface rainfall.
3. Animate the radar loop
A loop reveals three things: direction, speed and trend. Pick a recognizable edge of the rain area and watch it over several frames. Is it approaching your location? Is the band accelerating? Are new cells forming along the leading edge?
Do not extrapolate one pixel in a straight line for hours. Thunderstorms can grow, split, merge or collapse. A smooth forecast extension is a useful guide, not a camera view of the future.
4. Compare base and composite products carefully
NOAA describes base reflectivity as a low-elevation view commonly used to detect weather over a broad area. Composite reflectivity takes the strongest return found through multiple scanned heights. Composite can make a storm look more intense because it includes precipitation aloft that may not be reaching the surface.
5. Know what radar cannot tell you alone
- Radar cannot guarantee that precipitation is reaching your exact street.
- The beam rises above the ground with distance, so far-away echoes sample higher parts of storms.
- Buildings, terrain, insects and unusual atmospheric bending can create clutter.
- Radar intensity alone does not identify every hazard.
- Warnings from the responsible weather service should guide safety decisions.
A 30-second radar routine
- Confirm the location and newest observation time.
- Check the app's color legend.
- Play the recent observed loop.
- Estimate direction and arrival range, not an exact minute.
- Compare the hourly forecast and active warnings.
Frequently asked questions
What do the colors on weather radar mean?
They represent reflectivity according to the map's legend. Stronger returns are often shown with warmer colors, but palettes and thresholds differ between apps.
What does dBZ mean on radar?
dBZ is a logarithmic unit used for radar reflectivity. Higher values generally mean a stronger return from precipitation or other targets.
Can radar predict exactly when rain will start?
Radar animation can support a short-range estimate, but storms change and future frames are predictions. Treat arrival times as a range rather than an exact promise.
Sources and methodology
Feature claims were checked against official product and government pages on July 10, 2026. Editorial recommendations are based on the use cases described above; Weather Now is our product.
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