If September seemed wetter than usual in Metro Vancouver this year, that's because it was.
Three times as wet. Well, nearly.
"The fact is we had nearly 300 per cent of our rainfall," says Environment Canada Meteorologist Doug Lundquist. "There was 151 mm of precipitation in September. Normally there's only 51 mm."
"That's an incredible amount of rainfall."
For context, September is usually one of the drier months of the year, after July and August which usually get 36 and 37 mm respectively. September 2021 saw more than the average for that entire quarter of the year.
And this year, with the dry spring and summer we've had, more rain fell in September than the five months previous (April 1 to August 31).
While that only ranks as the sixth-most rainy September in Vancouver, Lundquist says the high amount is still interesting, given how much more than average fell. The total precipitation is more akin to the wettest months in Vancouver, landing between November (the wettest) and December (the second wettest).
"The fall monsoon season started a month or a month and a half early," he says.
He points to Sept. 17 when 51 mm fell in one day.
"The fact we get a whole month of rain in one day says a lot more than if we broke a daily record," Lundquist explains.
He notes that the sudden rain after a dry and hot summer may have made it feel even more extreme to some people.
Those two weather events might be connected through climate change, he adds, but he can't say with certainty.
"One of the things about climate change is that it creates warmer air, and warmer air can hold more water, and what goes up must come down," he explains.
Warmer temperatures over the Pacific this summer may also explain the heavy rain in September.
Just because Vancouver saw lots of water fall from the sky last month doesn't mean it will continue, he adds. While cooler temperatures are likely throughout the fall, predicting precipitation is more difficult and can't be narrowed down over medium timespans (like months).
Additionally, storms, which can bring lots of rain (like the one that dropped 51 mm) are smaller than the systems which affect temperatures and can be fairly specific in where they drop their water.
"You have to be right in the right track," Lundquist explains. "It's much more finicky than temperature."
