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“But if we get a repeat of all that heavy rain that we seemed to have been getting in the last couple of years, that’s going to give us peaks of the pest species later in the season,” said Fiona Hunter, a professor of veterinary and medical entomology at Brock University.

When is mosquito season in Ontario?

Overwintering mosquitoes — either those who hibernated over the winter or survived the cold as eggs — can appear as early as March when the weather begins to warm, said Rosalind Murray, an entomologist and assistant professor of biology at the University of Toronto.

Mosquito season begins to pick up in May, with bug populations typically peaking in late May to early June depending on rainfall and temperature. Mosquito numbers start dwindling in September as the weather cools, Hunter added. 

Cases of the mosquito-borne West Nile virus usually pop up between mid-April to November, , as that is when carrier species tend to be active.

How bad will mosquitoes be in Ontario this year?

Mosquito season is potentially off to a mild start this year following a chilly, dry spring, Murray and Hunter said.

“We generally think of two things when we’re trying to predict what’s going to happen with mosquito season,” Hunter said. “The first one is temperature and the second one is rainfall.”

º£½ÇÉçÇø¹ÙÍøaverages about 93 millimetres of precipitation every April, . But only about , nearly half of the historical trend.

For mosquitoes, “It’s all about standing water,” Murray said. “In April, we didn’t have a ton of rain, so it means that a lot of those temporary pools just dried right up — and that means there’s less habitat for those mosquitoes to breed in.”

Meanwhile, spots of and Ontario over the last month may have helped kill mating mosquitoes that overwintered as adults, Murray added: “Given that we had much cooler temperatures this spring ... we can probably expect that they won’t be as bad this May as they were last year.”

“º£½ÇÉçÇø¹ÙÍømight see slightly worse mosquitoes than other areas,” she noted, “because cities are a little bit warmer than their rural counterparts.”

While mosquitoes like the heat, they can’t take too much of it either: “You don’t want to heat up too quickly because then that sort of fries the mosquitoes,” Hunter said. “A nice slow, gradual increase in temperatures is what favors the mosquitoes. Not a sudden jump from winter to summer temperatures.”

Although mosquito season appears off to a slow start right now, excess rain could lead numbers of the bugs to spike down the line, as was seen in 2024 when flooding in º£½ÇÉçÇø¹ÙÍøled to a wave of West Nile virus-spreading mosquitoes, the experts said.

How to protect yourself from mosquitoes

Because mosquitoes breed in standing water, it’s important to empty out any pockets of water on your property.

“Common habitats in urban areas are flower pots, bird baths and gutters that are clogged,” Murray said. 

Otherwise, Hunter recommended covering up your skin with light-coloured, long-sleeved shirts and pants; mosquitoes are more attracted to dark colours, she said. You can also apply a , she added.