Mosquito Season Getting Longer In Minnesota

MINNEAPOLIS (WCCO) -- There are lots of things to celebrate about Minnesota summers, but mosquitos aren't one of them. Now there are signs that the mosquito season is actually getting longer.

In order to survive, mosquitos need warm and wet conditions in just the right combination. They die off in large numbers when temperatures fall outside of a 50-degree to 90-degree temperature range, and when relative humidity falls below 42 percent.

Temperatures in Minnesota have been warming over the last several decades, and the water content of the atmosphere has been increasing as well.

Those factors combined have lengthened the mosquito season by six weeks, according to Climate Central, a non-profit organization that researches climate change.

That's one of the largest increases in the nation. Examining data for over 100 U.S. metro areas shows that the average is closer to 10 to 20 days, and some cities in the southern U.S. have been seeing temperatures hot enough to decrease the overall length of the mosquito season.

During the last four decades here in Minnesota, autumn temperatures have warmed more than spring, meaning that many of those extra days are coming during the fall.

"They really do keep active until the first hard frost," Mike McLean, the communications coordinator for the Metropolitan Mosquito Control District, said.

That's changing how they deal with mosquitos.

"A lot of our workforce is seasonal -– you know, college students, people that are working in the summer," he said. "So it kind of means that they're available for not quite the length of time we need them, sometimes."

What they are fighting is changing, too.

"We're finding more and more of different species of mosquitos, that maybe we didn't have to worry about in the past, but that we see more and more kind of creeping northward with the change in the climate," McLean said.

A longer mosquito season is more than just an annoyance. Favorable conditions for mosquitos means the chance for spreading diseases -- such as West Nile Virus -- goes up.