Mayflies cover structures in Wisconsin

LA CROSSE, Wisconsin (NEWSCHANNEL 3) - It looks like something out of a science fiction movie. Swarms of mayflies are covering everything in a Wisconsin town.

They hatched over the weekend in La Crosse, Wisconsin, covering street lights, buildings, stairs and nearly anything in their path.

Mayflies are harmless and they hatch several times a year.

The National Weather Service says this weekend's swarms were so big they could be seen on radar.