Why Calgary's potentially 'normal' mosquito season might feel worse than it is

CBC

14-07-2025

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It's time to pull out the bug spray.
After a mild several years for mosquito activity in Calgary due to prolonged droughts, the periodic rain lately means the bloodsuckers are out in full swing.
Calgary entomologist John Swann said at best (or at worst, depending on how you see it), this is looking to be a "normal year" for mosquitoes.
But since we've had it easy in recent years, Calgarians might feel like they're swatting away mosquitoes more than they're used to.
And he warns it could get worse in the coming weeks.
"I look at the next two weeks and yes, sure enough, we're getting periodic rain maybe every three days. And that's what you need for summer mosquitoes," said Swann, who works at ABI Environmental Services.
"Now is the time to start getting cautious."
The City of Calgary, which monitors mosquito numbers each year, said the rainfall throughout June and warmer temperatures recently has resulted in an increase in mosquitoes. They expect it to peak by mid-July, but say the trapping data shows a typical number of mosquitoes for this time of year.
But some Calgarians say it's been quiet on the mosquito front until what seems like a recent explosion over the last week or so.
'They're just all over'
Calgarian Alan Chu noticed the sudden surge of mosquitoes in the last several days — and so did his family visiting from Ontario.
"The first couple of nights they were like, 'I can't believe you guys can just leave the doors open.' We don't have any screens on our back patio doors," said Chu.
"Then in the last couple of days, they're like, 'Oh, no, not so incredible,' because we started to get mosquitoes inside the house."
"They're the young, spry ones. They're just all over."
His wife doesn't like the smell of the chemicals in traditional bug repellents, so in recent days she's stocked up on other solutions.
"We put lemon eucalyptus essential oils on our skin … and use citronella candles or citronella essential oils," said Bonnie Larson.
Avoiding West Nile
Swann said he recommends practicing an abundance of caution at this time of the year.
"Even if you're not around the water, I would still be putting on repellents, wearing white clothing, long sleeves, trying to avoid dawn and dusk when mosquitoes are most actively feeding," he said.
But it isn't the itchiness of mosquito bites that bothers him the most — it's the risk of getting West Nile Virus.
He's particularly concerned now that the invasive northern house mosquito, a mosquito species that can carry diseases like West Nile, has been present in Calgary in recent years.
Researchers at the University of Calgary are calling on citizen scientists to study the potential health impacts of that species, which is known to be drought-resistant and likes human habitation.
"Even in a bad year, now we have a problem with this urban dwelling mosquito that transmits West Nile."
Swann predicts the mosquito season might last until the end of October, but that depends on how dry and cold it gets.