A colder start to spring in Canada means a potentially tamer introduction to allergy season, but experts warn that as soon as the weather starts to warm, it may bring an explosion of pollen into the air.
Allergy season usually follows the trend of tree pollen in the spring, grass in the summer and ragweed in the fall. And this year, Global News chief meteorologist Anthony Farnell warned that tree pollen and grass may hit allergy sufferers at once.
“April looks to be colder than normal across a huge chunk of the country, so there probably won’t be an early spring this year,” Farnell said.
“But with the sudden turnaround to summer-like warmth in May, we could get a really bad allergy season in some areas because all types of pollen will be peaking at once from trees, grasses and flowers. It’s something that has been happening more often in recent years especially in some parts of the U.S. when you get unusually warm temperatures for a prolonged period of time.”
About one-quarter of Canadians suffer from seasonal allergies, according to Dr. Anne Ellis, president of the Canadian Society of Allergy and Clinical Immunology. And the hardest-hit provinces tend to be British Columbia, Ontario and Quebec because of the trees — mainly birch — in the region.
Spring allergies shouldn’t pop up in these provinces until late April, but there is a caveat, she added.
“The exception would be if we had an unexpected sudden warming because that is a signal to the trees for them to really catch up on their maturation and pollination. So if we have a sudden warm-up at any point, expect really high pollen levels whenever that happens to be,” she said.
What will allergy season look like across Canada?
Pollen counts have been low across Canada so far this year, according to Daniel Coates, director of Aerobiology Research Laboratories.
The lab, based in Ottawa, monitors pollen and spores across Canada and predicts what allergy season may look like.
He said because of the cold start to the spring, many provinces are seeing lower pollen counts compared to previous years.
British Columbia
British Columbia’s spring usually starts earlier than the rest of Canada and this year the pollen count has been down 95 per cent compared to 2022, Coates said.
“Right now, it is very slow. We started sampling there in late January, early February and we’re averaging 95 per cent less pollen this year in the Vancouver area than we were last year at this time,” he said.
He predicts B.C. will see a slower allergy season in March and April, but it should be back to normal around May.
The Prairies
The Prairies usually have a later start to allergy season, Coates said, adding that this region may not experience anything out of the ordinary in 2023.
“It should start picking up in the next few weeks, but because it still has cooler weather it will be a little slower as well,” Coates noted.
Ontario
Last year at this time, the Greater Toronto Area (GTA) had high levels of pollen in the air, but it is currently “very low,” with only a small amount of maple and cedar pollen detected.
Coates predicts that allergy season in Ontario will be shorter because of the cold spring, but pollen levels could increase in May.
“(The trees) are sort of holding onto the pollen and as soon as it starts getting warmer, it will let loose. So we think it’ll be shorter, but it could be bad for a short period of time.”
Quebec
Quebec’s allergy season may parallel Ontario’s, Coates said. It may not be as “explosive” as Ontario but “definitely could be in a similar area, depending on the short-range weather,” he added.
Maritimes
Atlantic Canada’s allergy season is starting very slow, but this region typically has less pollen in the air than the rest of Canada, Coates said. He predicts the east coast to have more of a “normal” allergy season because of this.
Is allergy season getting worse because of climate change?
Although this year’s allergy season may be off to a slow start, experts say on average, pollen counts are increasing annually due to climate change.
This is because warm weather makes plants bloom and the pollen from trees, grass or weed tends to travel more under hot, dry conditions.
“We’re certainly seeing that climate change is impacting allergy season,” Ellis said. “It’s making the pollen seasons less predictable because of the fact that our weather is so much less predictable.”
Between 1990 and 2018, pollen levels across North America increased 21 per cent, according to a 2021 study published in the Proceedings of the National Academy of Sciences (PNAS).
The researchers found that pollen seasons are getting longer and more severe across the U.S. and Canada because of human-caused climate change, and argued that climate-driven pollen trends are likely to “further exacerbate respiratory health impacts in coming decades.”
Climate change affects allergy season in multiple ways. The higher temperature can extend the growing season, giving plants more time to emit pollen and reproduce. Carbon dioxide, meanwhile, fuels photosynthesis, so plants may grow larger and produce more pollen.
And due to warmer weather related to climate change, pollen season also starts earlier and ends later in the country.
Urbanization or city planning also has a role to play, Coates said, because a lot of cities prefer planting male trees over female trees to avoid having to clean up. Female trees don’t produce pollen but tend to create more of a mess from fruits and flowers. Distinctly male trees produce pollen but not seeds, pods and fruit, which fall to the ground.
— with files from Global News’ Saba Aziz