Live tree, grass and weed pollen data across Canada, updated daily. Canada’s pollen season is compressed into a shorter window than most countries, but birch pollen concentrations in Ontario and Quebec rank among the highest recorded in North America. This page tracks the pollen count for the 20 highest-allergy cities in Canada, ranked by today’s PollenIQ™ score. Enter your postal code below to check the pollen count in your area right now.
Highest Pollen Count Cities in Canada Right Now
The highest pollen count in Canada today is tracked across 20 cities selected from the Aerobiology Research Laboratories 2026 Pollen Report. Windsor, Ontario ranked as the worst city for pollen allergies in Canada in 2026, followed by Hamilton, Barrie, Victoria, and Kingston. Every city in this list is ranked live by its PollenIQ™ score, a composite index combining tree, grass and weed pollen levels plus local air quality. Scores update daily. The city at the top of this list has the worst pollen conditions in Canada right now.
Tree, Grass and Weed Pollen Count Across Canada
Canada’s pollen calendar does not follow one pattern. It follows the country’s geography. The Pacific coast, the Prairie provinces, Ontario and Quebec, and the Maritime provinces each have distinct pollen seasons driven by entirely different plant species. What triggers a severe reaction in Toronto may not exist at all in Vancouver, and vice versa. Knowing which type is active in your province today is the most useful information an allergy sufferer can have.
Tree pollen count in Canada
Tree pollen count in Canada is dominated by one species above all others: white birch. Betula papyrifera, the paper birch, is the most widespread tree in the country, growing from Newfoundland to British Columbia across a range that covers virtually every major Canadian city. Birch pollen season runs from March through May across most of the country, peaking in April in Ontario and Quebec when temperatures rise after the last frost.
British Columbia runs on a different tree pollen calendar. Alder is the primary early-season allergen in Vancouver and Victoria, releasing pollen from January through March before birch arrives. Victoria records one of the longest tree pollen seasons in Canada, with alder, birch, oak, and cedar each contributing at different points between January and June.
One fact that affects millions of Canadians beyond the sneezing and watering eyes: birch pollen cross-reacts with certain raw foods in a condition called oral allergy syndrome. Up to 70% of people with birch pollen allergy experience oral allergy syndrome, reacting to raw apples, pears, peaches, cherries, carrots, celery, and hazelnuts during pollen season. Cooking the food eliminates the reaction, but the raw form triggers itching and swelling of the mouth and throat within minutes.Tree pollen carries a 45% weight in the PollenIQ™ score, reflecting how consistently it dominates the first half of the Canadian allergy year from coast to coast.
Weed pollen count by Canadian province
Weed pollen count by Canadian province reveals a sharp divide at the Rocky Mountains. East of the Rockies, ragweed is the primary weed allergen. West of the Rockies, ragweed is largely absent.
Ontario and Quebec are Canada’s ragweed capitals. Windsor and Hamilton rank as two of the worst cities in the country for ragweed exposure, driven by the warm climate of southwestern Ontario, which closely mirrors conditions in the American Midwest. A single ragweed plant produces up to one billion pollen grains per season, and peak counts in Windsor during late August and September rival those seen in the worst US cities. Ragweed season in Ontario typically runs from mid-August through the first hard frost in October.
British Columbia tells a completely different story. Vancouver, Victoria, and most of BC have virtually no ragweed. The primary weed allergens in BC are mugwort and English plantain, which are present but significantly less potent than ragweed. For people moving to BC from Ontario or Quebec, the absence of ragweed alone can transform autumn from an unbearable season into a manageable one.
The Prairie provinces sit in between. Saskatchewan and Manitoba have some ragweed, but sagebrush and Russian thistle are more prominent weed allergens across the open plains. Climate data shows ragweed seasons are getting longer across North America, and southern Ontario has seen measurable increases in both ragweed pollen concentrations and the length of the ragweed season since 1995.
Grass pollen count across Canada
Grass pollen count across Canada is highest in the Prairie provinces. Alberta, Saskatchewan, and Manitoba sit at the centre of North America’s grassland ecosystem, where native fescue, wheatgrass, and brome cover millions of hectares with no natural break in coverage. When grass pollen season peaks across the Prairies in June, the flat, open landscape offers nothing to slow dispersal. Pollen moves freely across provincial borders.
Timothy grass is the dominant allergen in Ontario and Quebec, peaking in June and running through July. It is also the most allergenic grass species in Canada, causing stronger immune responses than most other grass types. Urban lawns, sports fields, and agricultural land extend grass pollen exposure significantly in the Greater Toronto Area and Montreal region, where managed turf covers enormous surface areas.
British Columbia’s wet climate and cooler temperatures moderate grass pollen compared to the Prairies and Ontario. That said, Aerobiology Research Laboratories monitoring data shows Vancouver still records moderate grass pollen counts each June, primarily from Kentucky bluegrass and perennial ryegrass in residential and park settings.
A timing difference most Canadians do not know: grass pollen season starts four to six weeks later in Canada than in equivalent latitudes in the United States, because Canadian springs run colder. The season is shorter but not necessarily less intense once it arrives.
When Is Pollen Season in Canada?
Pollen season in Canada runs from February through October, depending on where you live and which allergen you react to. It is shorter overall than in the United States, but the compressed timeline means multiple allergen types can overlap intensely during peak months. Research published in PNAS found that the North American pollen season now starts 20 days earlier and lasts 8 days longer than it did in 1990, with total pollen concentrations 21% higher over the same period. Canada is not exempt from this trend.
Tree pollen opens the Canadian allergy year. Victoria and Vancouver see alder pollen as early as January and February. Most of Ontario and Quebec do not see significant tree pollen until March, with birch peaking in April and tapering off by late May. In northern provinces like Manitoba and Saskatchewan, tree season does not begin in earnest until May, when spring arrives later.
Grass pollen follows from late May through August. June is the peak month across most of the country. In the Prairie provinces, grass season can produce extremely high counts during dry, windy June days when native grassland species release simultaneously. In Ontario and Quebec, grass and tree pollen overlap briefly in May, creating a period where multiple allergen types are active at the same time.
Weed pollen closes the season. In Ontario and Quebec, ragweed runs from mid-August through October. In BC, weed season is shorter and less severe. In the Maritime provinces, the first frosts arrive earlier, cutting the weed season short by September in most years. For most Canadians outside of BC, the allergy year ends with the first hard frost, typically in October.
Canadian Provinces with the Highest Pollen Count
The Canadian provinces with the highest pollen count are concentrated in two regions: the Ontario and Quebec corridor, and British Columbia for tree pollen specifically. The causes are different in each case, but both produce conditions that drive some of the most intense allergy seasons in the country.
Ontario carries the heaviest overall allergen load of any Canadian province. It runs all three major pollen types at significant levels across a long season. Birch and maple dominate spring, timothy grass peaks in June, and ragweed takes over in August. The Aerobiology Research Laboratories 2026 Pollen Report placed five Ontario cities in the top ten worst cities for pollen in Canada, including Windsor at number one, Hamilton at number two, Barrie at number three, Kingston at number five, and Kitchener in the top ten. Southwestern Ontario’s climate mirrors the American Midwest closely enough that conditions in Windsor are more comparable to Detroit than to Ottawa.
Quebec experiences intense birch and ragweed seasons. Montreal records some of the highest birch pollen counts in Canada during April, and the city’s ragweed season in August and September is among the worst in the country. The St. Lawrence River valley channels prevailing winds in ways that concentrate pollen over the city during peak season.
British Columbia ranks highest for tree pollen, specifically alder and birch. Victoria holds the record for the longest tree pollen season in Canada, running from January through June in most years. Aerobiology Research Laboratories ranked Victoria fourth in Canada for overall pollen severity driven almost entirely by its exceptional tree pollen season. The trade-off is that BC has virtually no ragweed, making autumn dramatically easier than in Ontario or Quebec.
Canadian Provinces with the Lowest Pollen Count
The Canadian provinces with the lowest pollen count share one defining characteristic: maritime climates. The Atlantic provinces, including Newfoundland and Labrador, New Brunswick, Nova Scotia, and Prince Edward Island, consistently record lower pollen levels than central and western Canada, driven by ocean winds, higher humidity, and shorter growing seasons that limit both the variety and intensity of pollen-producing plants.
Newfoundland and Labrador has the most limited allergy season of any province. The combination of a short, cool summer, sparse deciduous forest coverage compared to Ontario and Quebec, and persistent Atlantic winds that disperse and dilute pollen keeps counts lower than anywhere else in the country. Tree pollen is present in June and July, but grass and weed seasons are short and less intense than in most other provinces.
New Brunswick and Nova Scotia see moderate pollen seasons, primarily driven by birch and alder in spring and some ragweed in late summer. Counts are measurably lower than Ontario and Quebec, and the maritime influence shortens the ragweed season significantly by bringing early autumn frosts in September.
The Prairie provinces present a different picture. Saskatchewan and Manitoba have low ragweed levels compared to Ontario, but they compensate with intense grass pollen seasons in June driven by native grassland species. For people whose allergies are primarily triggered by tree pollen and ragweed, the Prairies offer some relief. For grass pollen sufferers, they do not.
No Canadian province is entirely pollen-free. Even in Newfoundland, birch and alder release pollen each spring. Tracking your city’s live PollenIQ™ score is the most reliable way to understand the specific allergen conditions in your location, regardless of provincial averages.
Pollen Count Canada: Your Questions Answered
Pollen count questions in Canada cluster around a handful of consistent themes. Whether you are tracking birch pollen in Toronto, ragweed in Windsor, or the grass pollen index in Calgary, the six questions below cover what Canadian allergy sufferers ask most about pollen tracking, the PollenIQ™ score, and how to read your hay fever forecast.
Questions about pollen counts and allergy seasons across the Canada
The highest pollen count in Canada shifts between cities depending on the season and allergen type, but Ontario consistently dominates the national rankings. The Aerobiology Research Laboratories 2026 Pollen Report ranked Windsor, Ontario as the worst city for pollen allergies in Canada, followed by Hamilton, Barrie, Victoria, and Kingston. Ontario cities occupied five of the top ten spots, driven by a combination of birch pollen in spring, timothy grass in June, and one of the most intense ragweed seasons in the country from August through October.
Windsor’s position at the top of the national rankings is not accidental. Situated at the southernmost point of mainland Canada, Windsor shares a climate with Detroit across the river. The city sits within the North American ragweed belt and records ragweed pollen counts in August and September that rival cities in the worst-affected American states.
For tree pollen specifically, Victoria and Vancouver record some of the highest birch and alder counts in the country. Victoria’s tree pollen season is the longest in Canada, running from January through June, with alder beginning in late winter before birch takes over in spring. Aerobiology Research Laboratories ranked Victoria fourth nationally, driven almost entirely by its exceptional tree pollen load.
Toronto is the city most Canadians search for pollen data on. As Canada’s largest city, Toronto’s pollen season is intense in spring, driven by a dense urban tree canopy of maple, birch, and oak. Ragweed season in late August is also significant, making Toronto’s allergy year one of the longest of any major Canadian city.
According to Aerobiology Research Laboratories, approximately 20 to 25 per cent of Canadians experience seasonal allergic rhinitis, commonly known as hay fever. The pollen index score in your city tells you more about your actual risk on any given day than a national ranking ever could.
Pollen is at its highest in Canada in May for most of the country, when birch pollen peaks across Ontario, Quebec, and the Prairie provinces simultaneously. But that answer changes significantly depending on your province and which allergen triggers your symptoms.
Tree pollen peaks first and earliest. In Victoria and Vancouver, alder pollen begins in January and February, making BC’s west coast the only part of Canada with a winter allergy season. In Ontario and Quebec, birch is the dominant early-season tree allergen, typically peaking in late April and early May. A single birch tree produces millions of pollen grains per day at peak season, and warm, dry days in May can push counts to extreme levels across the entire Great Lakes region.
Aerobiology Research Laboratories monitoring data shows that grass pollen peaks in June across most of Canada. The Prairie provinces record their highest grass pollen counts in the first two weeks of June, when native grassland species and agricultural crops release simultaneously during warm, dry conditions. In Ontario and Quebec, grass season overlaps with the tail end of tree season in late May, creating a brief window when multiple allergen types are active at the same time.
Ragweed defines the autumn allergy season in eastern Canada. August and September are the worst months for ragweed in Ontario and Quebec, with peak counts typically occurring in the third week of August. A single ragweed plant produces up to one billion pollen grains per season, releasing most of that between dawn and mid-morning on warm, dry days.
Research published in PNAS found that the North American pollen season now starts 20 days earlier and produces 21% more pollen than it did in 1990. For Canadians, this means May has become measurably worse over the past three decades, and the autumn ragweed season in Ontario now runs longer into October than it did in previous generations.
The Canadian provinces with the worst allergy season are Ontario, Quebec, and British Columbia, each for different reasons. Ontario and Quebec are worst for overall annual allergen load, driven by birch in spring and ragweed in autumn. British Columbia is worst for tree pollen specifically, with the longest tree pollen season in the country.
Ontario stands apart from every other province for the sheer length and variety of its allergy season. Spring brings birch and maple pollen across the province, with the Greater Toronto Area recording some of the highest urban birch pollen counts in Canada. June brings timothy grass at significant levels. August through October brings ragweed to southwestern Ontario at concentrations that rival the American Midwest. Aerobiology Research Laboratories placed Windsor, Hamilton, Barrie, Kingston, and Kitchener in the national top ten, making Ontario the most represented province in Canadian pollen severity rankings.
Quebec experiences intense birch and ragweed seasons. Montreal’s position in the St. Lawrence River valley concentrates prevailing winds over the city during peak pollen periods, amplifying both spring birch counts and late summer ragweed levels. Quebec City sees somewhat lower counts than Montreal due to its more northern position, but the birch season is still significant.
British Columbia ranks highest for tree pollen duration. Victoria records alder pollen from January and birch from March, giving the city a tree pollen season that runs six months. Vancouver’s spring birch season is one of the most intense in the country, though the complete absence of ragweed makes autumn dramatically more manageable than in Ontario or Quebec.
The Prairie provinces record intense grass pollen seasons in June but shorter and less severe ragweed exposure than Ontario. For people whose allergy symptoms are primarily triggered by ragweed, Alberta, Saskatchewan, and Manitoba offer significant improvement over life in Ontario.
The best Canadian province for allergy sufferers depends on which allergen triggers your symptoms. There is no single answer, but the Maritime provinces and parts of British Columbia consistently offer lower overall allergen exposure than central Canada.
Newfoundland and Labrador offers the lowest pollen burden of any province. The combination of a short growing season, limited deciduous forest compared to Ontario and Quebec, and persistent Atlantic Ocean winds that dilute and disperse pollen keeps counts lower than anywhere else in the country. Tree pollen is present in June and July, but grass and weed seasons are short and less intense. For people with severe ragweed allergies, Newfoundland’s relative absence of ragweed makes autumn genuinely manageable.
New Brunswick and Nova Scotia sit in the next tier. Maritime climates limit the length of all three pollen seasons, and the Atlantic provinces consistently record lower seasonal allergy severity than Ontario and Quebec in national health surveys. The trade-off is birch pollen in spring, which is present across all Atlantic provinces, though at lower intensities than in the Great Lakes region.
British Columbia presents an interesting case for ragweed sufferers specifically. Vancouver and Victoria have virtually no ragweed, which removes one of the most potent autumn allergens entirely. The trade-off is an intense tree pollen season from January through June in Victoria and from February through May in Vancouver. For people whose allergies are driven primarily by ragweed, moving from Ontario to BC can transform the quality of their autumn significantly.
The Prairie provinces are best for people whose primary allergy is to ragweed and tree pollen. Birch and ragweed are present but at lower levels than in Ontario. The significant downside is an intense grass pollen season in June driven by native prairie species covering millions of hectares.
No Canadian province is entirely pollen-free. The most reliable approach is to track the live pollen index score for your specific city rather than relying on provincial-level generalisations that mask significant local variation.
Birch pollen is so bad in Canada because white birch is the most widespread tree in the country, and it is one of the most allergenic tree species in the world. An estimated 20 to 25% of Canadians suffer from seasonal allergic rhinitis, and birch pollen is the single largest contributor to spring hay fever across most of the country.
White birch grows from the Atlantic coast to the Pacific, covering a range that includes virtually every major Canadian city. Unlike oak, which dominates the American Southeast, or cedar, which defines Texas winters, birch is Canada’s universal allergen. There is no region of the country where it is entirely absent.
Birch pollen is also exceptionally fine. At approximately 20 micrometres in diameter, birch pollen grains travel easily on wind currents over long distances. On peak days in May, birch pollen from rural Ontario forests can reach Toronto’s downtown core at significant concentrations even when there are few birch trees in the immediate vicinity.
The most significant and least understood consequence of birch pollen allergy is oral allergy syndrome. Up to 70% of people with birch pollen allergy develop oral allergy syndrome, experiencing itching and swelling of the mouth, lips, and throat when eating certain raw foods including apples, pears, peaches, cherries, plums, hazelnuts, almonds, carrots, celery, and raw potato. The reaction occurs because the proteins in these foods are structurally similar to birch pollen proteins, causing the immune system to respond to the food as if it were pollen. Cooking destroys these proteins and eliminates the reaction.
Research published in PNAS confirms that North American pollen seasons are starting earlier and producing 21% more pollen than in 1990, and birch is among the species most affected by warmer springs. Canadian birch seasons are beginning earlier each decade as spring temperatures rise, compressing the gap between snowmelt and peak pollen release.
Pollen season in Canada does not end on one date. It ends in three stages, and the timing depends heavily on which province you live in and which allergen type you react to. For most Canadians, the allergy year runs from March through October, with a brief period of relief in November before winter sets in fully.
Tree pollen season ends first. In most of Ontario, Quebec, and the Prairie provinces, tree pollen wraps up by late May or early June as birch, maple, and ash complete their pollination cycles. In British Columbia, tree season runs considerably longer. Victoria’s alder and birch season can extend into June, giving BC residents the latest tree pollen end date in the country. Aerobiology Research Laboratories monitoring data shows Victoria recording measurable tree pollen counts as late as early July in warm years.
Grass pollen season ends by late summer. In most provinces, grass pollen drops significantly by August as cool nights begin limiting pollination. The Prairie provinces see grass season end earliest, typically by late July when overnight temperatures fall. In Ontario and Quebec, grass season occasionally extends into August during warm summers.
Ragweed defines how late the eastern Canadian allergy year runs. Ontario and Quebec ragweed season ends with the first hard frost, which typically arrives in late September or early October across most of the province. EPA climate data shows the ragweed season has grown by up to 21 days in northern locations since 1995, driven by later autumn frosts. In Windsor and Hamilton, ragweed can persist well into October in mild years.
British Columbia’s pollen year ends earlier than most provinces. Without ragweed as a primary autumn allergen, BC residents effectively reach the end of allergy season when grass pollen drops in August. For most of the province, the allergy year is over by September.
Tracking the PollenIQ™ score for your city through autumn tells you exactly when your local season ends. When the score drops to Very Low for several consecutive days following a frost event, pollen season in your area has effectively ended until the following spring.