Scientists recently obtained photographic proof that thunderstorms create invisible ultraviolet blue sparks on trees.

Beginning nearly 100 years ago, scientists began speculating that weak electrical discharges from thunderstorms may appear on plants. Lab experiments over the last 50 years demonstrated how the charge of a thunderstorm induces an opposite charge from the ground below. The idea is that the ground charge is attracted to the charge above it, and will travel toward the highest point it can reach: leaves on trees.

Light-Emitting Leaves

During a thunderstorm in North Carolina in 2024, researchers saw weak electrical discharges called coronae on the tips of leaves. This led them to theorize that thunderstorms may cover entire tree canopies with a blue glow, too faint for human eyes to perceive.

This could also burn the very tips of leaves, which could harm the tree canopy and could have shaped tree evolution.

“These things actually happen; we’ve seen them; we know they exist now,” Patrick McFarland, a study co-author and meteorologist at The Pennsylvania State University, explained in a statement. “To finally have concrete evidence [of] that…is what I think is the most fun.”

To capture proof of the phenomenon, the team of researchers piled into a minivan with a weather station, an electric field detector, a laser rangefinder, and a roof-mounted periscope that could detect light through an ultraviolet camera. This allowed researchers to detect the presence of the coronae using their UV emissions.

The team watched a video feed from inside their car. When they analyzed the video, they saw 41 coronae on leaf tips in the span of 90 minutes.

According to McFarland, someone with superhuman vision could “see this swath of glow on the top of every tree under the thunderstorm. It’d probably look like a pretty cool light show, as if thousands of UV-flashing fireflies descended on the treetops.”

The findings are detailed in a study recently published in the journal Geophysical Research Letters.