Why Is Weather Radar Empty When It's Raining?

It's a classic frustration: rain is falling on your window, you open a radar map — and it's blank. The radar isn't broken. It's running into the physical limits of how radar works.

Radar beams go straight; the Earth curves

A radar site fires its beam outward in a straight line, tilted slightly upward. But the Earth's surface curves away beneath that beam. So the farther you are from the radar, the higher above the ground the beam is travelling.

Close to a radar, the beam samples rain near the surface. A few hundred kilometers away, that same beam might be a kilometer or more up in the sky — sailing clean over low clouds and light rain that never get detected. This is the single biggest reason radar looks empty during real rain.

Other things that create radar gaps

• Terrain blocking — mountains and hills physically block the beam, leaving "shadows" with no coverage behind them.
• Shallow precipitation — drizzle and light, low snow often sit entirely below the beam, especially at a distance.
• Coverage holes — oceans, remote regions and some countries simply have few or no radar sites, so there's nothing to see.

The fix: pair radar with satellite

This is exactly why LEV pairs radar with satellite cloud imagery. When radar misses low-level rain, satellite still shows the cloud overhead — so between the two layers, you can tell the difference between "no rain" and "rain the radar can't see."

Open the live map, switch on both layers, and you'll rarely be fooled by an empty radar again.