1. Virga: precipitation evaporates before landing
The National Weather Service defines virga as precipitation falling from a cloud that evaporates before it reaches the ground. Radar can detect the drops or ice crystals aloft even while the air below the cloud remains dry.
This is common when the lower atmosphere is dry. As precipitation falls into that layer, evaporation cools the surrounding air. Virga is usually simply an explanation for the mismatch, although strong evaporative cooling can sometimes contribute to gusty downdrafts.
2. The radar beam is above your neighborhood
A radar beam travels upward relative to the surface as distance from the radar increases. Far from the site, the lowest scan may sample precipitation thousands of feet above the ground. The app places that return on a flat map, which can make it look like rain is occurring at street level.
3. You are looking at an older or predicted frame
Check the timestamp and timeline. The shower may have weakened after the latest observed frame, or the map may have crossed into future radar. Forecast animation is an estimate, not a new measurement.
4. Ground clutter and biological targets
Radar can receive energy from buildings, terrain, insects, birds or anomalous propagation. Many systems filter these targets, but filtering is imperfect. Clutter often appears nearly stationary across the loop, forms close to a radar site or has an unnatural shape.
5. Melting snow can look stronger than surface rain
As snowflakes melt, they can produce a band of enhanced reflectivity known as the bright band. Composite products can also select the strongest return found aloft. Both effects may exaggerate the precipitation you experience at ground level.
How to diagnose the mismatch
- Confirm that the timeline is on the newest observed frame.
- Play the recent loop and see whether the echo moves naturally.
- Check humidity and the surface observation nearby.
- Compare base reflectivity with composite reflectivity if available.
- Look outside, but keep official warnings active during severe weather.
Radar is not “lying.” It is measuring a volume of atmosphere. The map becomes easier to trust once you remember that the measurement may be above you and that not every detected target is rain reaching the pavement.
Frequently asked questions
What is virga?
Virga is rain or snow that falls from a cloud but evaporates or sublimates before reaching the ground.
Can radar detect clouds?
Weather radar mainly detects precipitation-sized targets and other scatterers. Ordinary cloud droplets may be too small to create a useful echo on a typical precipitation radar.
Why does radar show snow when none is falling?
Snow may be falling aloft into dry air and sublimating before it reaches the surface, or the beam may be sampling well above your location.
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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