Spotted Lanternflies Are So Dense They’re Showing Up on Weather Radar

Weather radar across the mid-Atlantic lit up with vivid colors on Thursday—typically a sign of rain. But skies were clear. The real cause? A massive swarm of spotted lanternflies.

These invasive insects, originally from Southeast Asia, are now so abundant in parts of the U.S. that they’re being picked up by weather radar. Capable of riding air currents as high as 3,000 feet, the lanternflies are becoming an increasing threat to agriculture, particularly vineyards, fruit trees, and hardwoods.

Experts urge the public to kill lanternflies on sight, but the sheer size of the swarms—now visible from miles away—makes that easier said than done.

How Radar Detected the Swarm

Meteorologists used three key types of radar data to confirm it wasn’t rain:

Reflectivity measured material in the air at levels comparable to a moderate rainstorm.
Correlation coefficient helped determine the shape of the airborne objects. Unlike uniform raindrops, the radar returned more irregular patterns—consistent with insects.
Velocity readings showed the mass was drifting south-southeast, suggesting they were being carried by light winds, not flying under their own power like migrating birds, which also tend to move at night.

While it’s not unusual for insects to appear on radar—such as a butterfly migration over Oklahoma in 2019 or cicadas near Washington, DC in 2021—this marks another troubling sign of the lanternfly’s spread. Last September, a similar radar event occurred near Pittsburgh, according to CBS News.

With lanternflies now filling the skies in detectable numbers, experts worry the problem is reaching a new scale.

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