On Tuesday evening, the National Weather Service office in San Diego picked up not rain on the radar, but a group of ladybugs called a "bloom."
The array of beetles were spread throughout the sky rather than packed into a clump, flying between 5,000 feet and 9,000 feet, NWS meteorologist Joe Dandrea told the Los Angeles Times.
However, a phenomenon of bugs showing up on the weather radar isn't as uncommon as you would think.
The weather radar is powerful enough to pick up on bats, birds, butterflies and even pollen moving through the atmosphere. The trick is differentiating weather from animals.
"Radar works by sending a pulse of energy through the atmosphere, and when that pulse of energy encounters an object in the atmosphere like a raindrop, some of that energy in the pulse will bounce back to the radar itself," AccuWeather meteorologist Brian Lada explained.
The NWS uses a dual-polarization weather radar, which sends pulses of energy through the atmosphere horizontally and vertically.
By using these two versions of energy pulses, "we can tell more information about the objects that it encounters when that pulse of energy hits an object in the sky," Lada said.
From these more detailed readings, meteorologists can see rain, large hail or in this case, ladybugs.
The chances of picking up animals on the radar are higher when the weather in the area is dry.
It's possible for meteorologists to tell the difference between precipitation and a swarm of animals on the screen from how the readings move to the shape they form.
"If the radar is detecting a colony of bats moving through the sky, that's going to look different than it would raindrops in the atmosphere," Lada said.
For Lada, he was able to discern the blotch as something other than precipitation by the way that it traveled. He described the direction in which it was moving as "odd," compared to California's normal weather patterns. June is also typically a dry time of the year for Southern California.
When the San Diego office of the NWS saw the blotch, they called a ground spotter, who confirmed it wasn't precipitation, but ladybugs.
Although no one has been able to identify the type of ladybugs blooming on radar, convergent ladybugs are the most common type in the state, according to the National Park Service. From late May to early June, they usually migrate to the mountains to feed on aphids and pollen.
According to the NPS, the beetles usually fly on windless days and have a minimal flying temperature of at least 55 degrees F.