If you’re prone to ragweed allergies, you may notice the sniffles, red eyes and other day-to-day annoyances come a little early this year, due to a combination of a highly specific set of weather factors.
Across most of Canada, the summer has been marked by prolonged stretches of extreme heat and dry conditions, but in Ontario and Quebec, a well-timed (or poorly-timed, depending on how you view it) series of steady and frequent rains and humidity in recent weeks has meant the start of ragweed season may be a little more intense this year.
“It’s starting at about the same time as is typical for Ontario and Quebec, but the levels are getting a bit higher than we normally see at this time of the year,” said Dawn Jurgens, Director of Operations for Aerobiology Research Laboratories.
“Usually we don’t see such … levels like that until a little bit later in August, once it starts to cool down a little bit more. But it’s still quite warm, so we think it’s probably due to the wetness, encouraging more of the weed growth.”
The development of particular kinds of weeds like ragweed relies on the weather during their own particular growth window, rather than how the entire season leading up to it unfolds.
Ragweed, for example, won’t be found in June, and usually begins to grow some time in July, coinciding this year with the summer wet patches in Ontario and Quebec. Ragweed also occurs in Atlantic Canada and as far west as Saskatchewan, while being largely absent from Alberta and British Columbia.
As for the rest of the season, Jurgens says if warm conditions persist, and even if followed by a cool-down accompanied by regular rain, it will likely be a “fairly high” ragweed season.
“So if it’s a typical September coming up, we will probably see an average or even above-average ragweed season this year,” Jurgen says, adding that though ragweed levels do drop off, the plants can reduce pollen as late as the first frost.