What happens when in Quebec, the short answer
In Quebec, three pests genuinely follow the seasons, wasps, rodents and carpenter ants. The rest, bed bugs and cockroaches first among them, live indoors all year and ignore the calendar entirely. Here is the overview, then the month by month detail.
| Period | What becomes active | What to do |
|---|---|---|
| January to March | Bed bugs, cockroaches, rodents already inside | Treat now, do not wait for spring |
| April and May | Ants, the first queen wasps scouting sites | Fix the moisture and the rotten wood |
| June | Carpenter ants become visible, fleas arrive with outdoor pets | Treat early, before the colony grows |
| July | Quebec's July 1 moving day, bed bugs travel | Inspect before you move in |
| August | Wasps turn aggressive, rodents look for shelter | Have nests removed, start sealing |
| September | Wasps at their peak, spiders and rodents moving in | Finish sealing before the frost |
| October | Last sealing window of the year | Seal, clear the garage and the shed |
| November and December | Everything happens indoors | Watch for the signs, react fast |
January to March, everything happens indoors
Winter solves nothing. It concentrates. Pests that were already in the building end up warm, fed, without competition, and they keep breeding quietly while you wait for spring.
The bed bug is the perfect example. According to the Government of Quebec, it measures 4 to 7 mm, normally lives 5 to 6 months, survives more than a year without feeding in a dormant state, and its eggs hatch 10 to 14 days after being laid. It slips into a gap the thickness of a credit card. None of that depends on the season.
This is also the most comfortable time to treat, the home is occupied, heated, and the preparation happens calmly. According to the INSPQ, a single treatment is not enough, the half-life of registered insecticides is too short to kill the bugs hatching from eggs. Expect a second application 2 to 6 weeks later and a follow-up visit 2 to 4 weeks after each one.
What this means in practice. Do not push it to spring. Three months of waiting hands the insect several generations of head start. Our preparation checklist before treatment covers the rest.
April to June, moisture wakes the carpenter ants
At thaw, water gets in. A dripping roof edge, a waterlogged window sill, a porch beam that stayed wet all winter. That is exactly what a carpenter ant is looking for.
According to the Montreal Insectarium, the colony is built around a main nest, always close to a source of moisture, plus sometimes up to a dozen satellite nests. The most common cause of a house infestation in Quebec is precisely a satellite nest forming, with no queen in it. Galleries are carved into wood softened by moisture, and the visible sign is a small pile of sawdust that keeps coming back in the same spot.
What matters in spring is not killing ants first, it is finding the water. Dry wood interests nobody. The full list of signs is in our article on carpenter ant satellite nests.
This is also when pets go back outside and bring fleas home, and when the first queen wasps pick their spot. A nest caught in April fits in one hand. The same nest in September takes a full intervention.
July, moving month, and the worst time for bed bugs
Quebec's July 1 moving day has no equivalent in North America. Tens of thousands of homes change hands on the same day, with shared trucks, furniture picked up off the sidewalk and boxes travelling from one building to the next. For a bed bug, that is free transport.
The Government of Quebec is explicit, bed bugs spread during house moves, through second-hand items bought at flea markets and thrift stores, and through furniture found in the street. Its moving recommendations are concrete.
- Ask the movers in advance what measures they take against bed bugs.
- Seal your belongings in plastic bags and tape the cardboard boxes shut.
- Inspect the truck before loading.
- On arrival, inspect the rooms of the new home with a flashlight before setting anything down.
- Second-hand furniture gets inspected before purchase, carried in a sealed bag and steam treated before it comes in.
The rule that saves the most people fits in one sentence. A mattress picked up off the sidewalk in July costs more than a new one. In Montreal, a discarded mattress must in fact be wrapped in a plastic cover and slit open, precisely so nobody takes it home.
August and September, wasps turn genuinely aggressive
It is not your imagination. According to the Montreal Insectarium, wasp populations peak in late summer and early fall, and the colonies break down completely every year until the workers die with the first frosts. That is when they stop hunting insects and start looking for ripe fruit and sugar, which is why they show up around plates and cans.
Health Canada confirms they are more aggressive in late summer and harder to control, the German yellowjacket being the most aggressive species. It recommends spraying after nightfall, when wasps are less active, and calling a professional to remove the nest.
Our guide on wasp nests sets out which cases can wait for the frost and which cannot.
August to October, rodents look for their winter shelter
From late summer until the first frosts, mice look for somewhere warm and dry. They force nothing, they use what is already there, a gap under a garage door, the edge of a pipe, a torn basement window screen, a cracked foundation joint.
That is the sealing window, and it closes in October. Sealing a house with no rodents in it is maintenance work. Sealing a house that already has them locks them inside, so treatment has to come first. The full method is in our article on sealing entry points before October.
On the health risk, proportion matters. According to the Government of Quebec, hantavirus infection is rare, six cases reported since 2005, the year of the first case in Quebec. It spreads by inhaling particles contaminated with the urine, droppings or saliva of infected rodents, particularly while cleaning closed or poorly ventilated spaces. The instruction that counts is to never sweep or vacuum rodent droppings. Our safe cleaning guide sets out the method.
The pests that ignore the calendar completely
Two problems have no season in Quebec, and they are the ones that generate the most calls. Bed bugs and cockroaches live indoors, in the warmth, all year round.
The figures from Montreal's regional public health department, published in 2019 from the 2017 Housing Survey, show where the problem concentrates. In 2017, 2.8 % of households on the island of Montreal reported a bed bug infestation, roughly 24,000 households. Prevalence reached 4.0 % among tenants against 0.7 % among owners, close to six times less. It climbed to 6.3 % in buildings of 12 units and more, against 1.9 % in buildings of 5 units and fewer.
In other words, the bigger the building, the more frequent the problem, because an infestation travels from one unit to the next. That is why the City of Montreal requires an exterminator notified of an infestation to inspect the entire building, not only the unit that reported it.
In a rented home, who does what, in any season
The question comes up all year, so let us settle it here. The Administrative Housing Tribunal explicitly lists cockroaches, bed bugs, ants, rats and mice among unsanitary conditions, and the landlord must keep the dwelling in good habitable condition.
On the tenant side, the City of Montreal is clear, you do not treat it yourself and you notify the landlord immediately. If nothing happens, you call 311. On the exterminator side, every bed bug treatment must be declared to the City within 5 days, under by-law 03-096.
The full picture, with real Tribunal rulings, is in our article on who pays the exterminator in Quebec. Every situation turns on its own facts and none of this is legal advice.
The one habit that changes everything, whatever the date
A pest caught early costs less, treats faster and usually ends with one extra visit. Caught late, it becomes a multi-visit job, with heavy preparation and sometimes an entire building to treat.
In practice that means three appointments a year. In spring, a walk around the house looking for water and rotten wood. In late summer, sealing the entry points. And in winter, you do not let anything slide indoors on the excuse that the season is quiet.
Axion works across 57 zones in the Greater Montreal area, with CD5/CD6 certified technicians, products registered by Health Canada and a written guarantee. Our eight extermination services cover this whole calendar, and you will find your area on the service areas page.
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Frequently asked questions
What is the worst month for pests in Quebec?
There is no single worst month. August and September stack the most situations at once, wasps at their peak according to the Montreal Insectarium and rodents looking for shelter before the frost. July is the worst moment for bed bug spread, because of Quebec's July 1 moving day.
Are bed bugs seasonal?
No. They live indoors all year. The Government of Quebec states that a bed bug normally lives 5 to 6 months and survives more than a year without feeding in a dormant state. Winter does not kill them, it concentrates them in the warmth with you.
Should I wait for winter to kill the wasps?
Sometimes yes, sometimes no. According to the Montreal Insectarium, colonies break down every year until the workers die with the first frosts. But a nest near a door, inside a wall or along a walkway has to be removed now, especially if someone in the household is allergic.
When should I seal my house against mice?
Between late August and October, before the first frosts. After that, the cold has already pushed rodents indoors and sealing would lock them in. In that case you treat first, then close the entry points.
Why treat in winter instead of waiting for spring?
Because indoor pests keep breeding in the warmth. According to the INSPQ, bed bug eggs hatch in 10 to 14 days and a single treatment is not enough. Three months of waiting hands the insect several generations of head start.
Can I remove a wasp nest myself?
Health Canada recommends calling a professional to remove the nest, and notes that wasps are more aggressive in late summer. The work is done after nightfall, when they are less active. This is the classic multiple-sting situation.
Does this calendar apply to an apartment building?
The periods are the same, but the frequency changes. According to Montreal public health, bed bug prevalence reached 6.3 % in buildings of 12 units and more in 2017, against 1.9 % in buildings of 5 units and fewer. A building is treated as a whole, never unit by unit.