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NH Health

Record rain and mosquitoes ‘a window into the new normal’

More rain means better habitat and conditions for the insects looking for blood meals

Warmer temperatures, more rain, and stagnant water create more habitat for mosquitoes.OLIVIER MORIN/AFP via Getty Images

CONCORD, N.H. — This summer has brought record rainfall to the Hubbard Brook Experimental Forest in the southwestern corner of the White Mountain National Forest.

The 8,700-acre forest received 23 inches of rain over the past three months, the highest ever for that time frame since researchers started measuring rainfall there 68 years ago.

The rain has also brought hordes of mosquitoes to the region.

“There are definitely more mosquitoes outside my tent than in most years,” said Matthew Ayres, a professor of biological sciences at Dartmouth who studies population ecology of insects and focuses on forest pests to understand how species fluctuate.


Ayres said the relationship between rain and the mosquitoes is simple: more rain creates extra habitat for larval mosquitoes resulting in more adult mosquitoes flying around and trying to get blood meals from people and other animals.

And, he said, we should prepare for these damp and mosquito-ridden conditions to become more common in future years.

“This is a window into the new normal,” he said.

Climate models have consistently predicted that the Northeast will become warmer and wetter, with more extreme rainfall events. At Hubbard Brook, 17 of the past 20 summers have been wetter than normal, receiving more than 15 inches of rain, which is the long-term average, according to data from the research station.

With climate change, new kinds of mosquitoes are coming to New Hampshire carrying diseases like West Nile Virus and Eastern Equine Encephalitis.

There are several species of mosquitoes belonging to a genus called Culex that are vectors of these diseases, Ayres said. Their distributions are expanding to the north as the climate warms.

Some of those species can already be found in New Hampshire, but Ayres said they will become more abundant and established in the future, increasing human exposure to the diseases they carry.


“They’re knocking on our door,” he said. “Outside the tent where I’m sitting now, there’s a rising tide of new species that are colonizing these forests.”

In his research, Ayres found that warmer weather also impacts mosquitoes. In 55 degree weather, mosquitoes took 20 days to mature, while at 75 degrees, it took them less than 10 days.

And mosquito season is growing longer. Research shows that fall is coming later, increasing the number of days when mosquitoes abound.

The state of New Hampshire collects mosquitoes to test for diseases like West Nile Virus and Eastern Equine Encephalitis.

Sarah MacGregor is an entomologist who owns Dragon Mosquito Control in Stratham, one of the companies the state contracts with for mosquito collection.

“I’m chained to the microscope this year because there’s so many mosquitos in our traps,” she said. “It’s certainly heavier than we’ve seen in quite a while and that is all due to the rain.”

Last summer, drought conditions spread throughout much of the state, which kept mosquito populations lower. With the rain this year, their populations have soared.

“Mosquitoes are breeding everywhere this year,” MacGregor said. “You name it, we’re finding mosquitoes: Woodland pools, salt marshes, they’re everywhere.” She said they’ve even found mosquitoes breeding in roadside litter, like a takeout container.

Throughout the course of mosquito season, there are anywhere from 40 to 45 mosquito species in New Hampshire, according to MacGregor. They usually wane in August, but not this year.

“We’re pooling more mosquitoes in August than I’ve ever done,” said MacGregor, who has been working with mosquitoes for 45 years. Her lab was still seeing about a dozen mosquito species at the end of summer, which is abnormally high.


She said high numbers going into fall could mean more disease next year. At home, she said people should dump out any water that’s collecting in their yard or around their home as that’s where mosquitoes breed.

Cases of the diseases have occurred in New Hampshire between the end of July and the end of September, according to the Department of Health and Human Services. There is no specific treatment and no human vaccine.

In 2003, there were three human cases of West Nile Virus, and everyone survived. Between 2005 and 2010 there were 11 cases of human EEE, leading to two deaths. West Nile Virus was first detected in New Hampshire in August 2000, and there was one recorded case of a human contracting the disease in 2017, according to a 2023 department surveillance, prevention, and response plan.

MacGregor said this year her team is only finding mosquitoes that carry Jamestown Canyon virus. It was first reported in New Hampshire in 2013, according to the department.

The department recommends taking preventative action against these diseases, like avoiding mosquito bites and mosquito-proofing your home. That includes getting rid of excess water that’s gathered in buckets, cans, pool covers, flower pots, and tires, and cleaning out clogged rain gutters. Make sure window and door screens are in good condition.


Protective clothing can also be an effective shield, including long pants, long-sleeved shirts, and socks. Mosquitoes are most active between dusk and dawn, which is a good time to limit outdoor activity. Using a repellent can also help reduce mosquito bites.

Amanda Gokee can be reached at Follow her @amanda_gokee.