Biologist says Mayfly hatch could be late, but huge this year

Cooler waters delay the hatch which usually happens around July 4.

Soon enough, the mayflies will swarm as you, perhaps try to get gas, or venture out near the Mississippi River. 

So far, however, there’s only been one mayfly seen by Mark Steingraeber.

The retired fish and wildlife biologist, who lives in the bluffs of La Crosse County, said it was just a lonely male.

“Probably looking for a mate, but he couldn’t find any up here,” Steingraeber said.

The rest are coming. And Steingraeber thinks it might be a little later than this season but it could be a big hatch.

“Just due to those high river stage and just the huge quantity of additional water we have, sometimes it just takes a little bit loner for the water to warm up,” he said. “Last year we didn’t see a really pronounced emergences anywhere up and down the upper Mississippi River, as we have in previous many years. 

“Quite often those years are followed by a large emergence.”

Mayflies need warm water to begin hatching, which usually takes place round July 4. Two years ago at this time, La Crosse had a big hatch large enough to be seen on radar (above right). You can see this year’s and past mayfly hatches from the National Weather Service here.