They're calling it frog-ageddon.

The population of northern leopard frogs in one area of Vermont has exploded in recent days, thanks to a rainy spring that left prime hatching grounds for the tiny, spotted green amphibians.

Jim Andrews, director of the Vermont Reptile and Amphibian Atlas, said millions of the frogs have covered lawns, fields and swimming pools, and just about anywhere else.

"These guys were popping out of the grasses; As you drove, they were popping off the roads," Andrews told weather.com.

(MORE: This Is How a Heat Wave in California Is Affecting Your Guacamole)

They've also been squashed en masse by cars on the asphalt. Andrews estimated that at least 400,000 of the frogs have been killed on a half-mile stretch of road in Salisbury, where the sudden amphibian baby boom has surprised locals. Andrews is a resident of the area as well.

He said an unusually wet spring, and more rain than usual in recent years, fueled the frog frenzy.

"I suspect that this is a climate change event," Andrews said. "In general, we've been getting more and more rain and bigger rain events."

The first half of 2019 was the fourth-wettest on record for the state of Vermont, according to NOAA data that goes back to 1895.

Also, temperatures have been slightly cooler than average, according to NOAA, which may have led to less evaporation of water out of the ground.

All that rain, combined with a large winter snowpack and the lack of drying out, left fields along a river called Otter Creek soaked with water longer than usual, Andrews said. So much so that local farmers couldn't plant their feed corn or alfalfa this year, and the frogs had free rein.

"What happened was that whole area stayed covered in water – it didn’t dry out," Andrews said. "This has happened more and more lately ... so this particular (frog) population has been growing, and this year, we just dished out these perfect environmental conditions."

(MORE: College Student Makes Discovery of a Lifetime in North Dakota: the Skull of Triceratops Named Alice)

Craig Zondag, the Lemon Fair Insect Control District’s field coordinator-biologist, has been observing the floodplain for 11 years. Zondag told the Addison County Independent that the frog inundation was "unprecedented."

"It seemed like it was biblical in proportion," he said of one recent day. "If they were falling from the sky, it would have been a plague."

Zondag said northern leopard frogs can hop as far as four to five miles from where they were hatched.

"They have tremendous mobility and endurance," he said. "It makes me wonder if all those frogs survived, how that would play out in the broader ecosystem."

But they're also at the bottom of the food chain, and are a treat for herons, hawks, owls, snakes, raccoons and other wildlife in the area.

"It's a buffet for the predators," Andrews said.

He said the density of frogs has thinned out since last week because they are radiating out to other areas. He's not entirely sure why they are on the move, but he says it's likely a combination of two things that the frogs instinctively know.

First, they can't survive at such a high density. And the second?

"They know their bigger parents, grandparents, aunts and uncles will eat them."