May 29, 2023

May ends on an odd note with 90s in Canada and 60s in the Carolinas

Things are a little wonky when it's 90°F in northern Canada and only 66°F in Knoxville, Tennessee.

Just about everyone who lives in the southeast or Mid-Atlantic is familiar with the low-pressure system that's brought uncharacteristically cool weather for the end of May.

This system is part of a larger pattern that's flipped eastern North America's conditions upside down, giving the northern U.S. and eastern half of Canada a spell of summer-like warmth while those of us farther south are mired in a gloom worthy of early March.

Monday afternoon only managed to climb into the mid- to upper-60s across large swaths of Tennessee, Virginia, and the Carolinas, with a few areas that managed some breaks in the clouds groaning above the 70-degree mark. It's been cool and rainy like this for days as a suspiciously wound-up low-pressure system moseyed just off the North Carolina coast.

Temperatures coming in 10-15+ degrees below normal are bad enough at the end of May—and even worse when it's the Memorial Day weekend—but the real kicker in this pattern is that folks up north, all the way north, experienced unusual temperatures in the other direction.

Source: Environment and Climate Change Canada

Fort Severn is a tiny outpost on Hudson Bay in far northern Ontario where the average temperature is "her eyeballs are frozen, Clark," for seven months of the year.

The temperature at that airport on Monday, May 29, climbed up to almost 90°F, according to Environment Canada, which is just as impressive in Celsius (32.2°C) as it is in Fahrenheit.

Conditions got even warmer in Fredericton, New Brunswick, on Sunday, a burst of summertime heat that fueled devastating wildfires in Nova Scotia. 

Source: Tropical Tidbits

This atmospheric flip-flop bathed the eastern half of North America courtesy of a pattern called a Rex block, named after the meteorologist who discovered the pattern back in the '50s. These setups occur when a ridge of high pressure aloft gets jammed in place beneath an upper-level low to its south.

A Rex block doesn't go anywhere in a hurry. These two features get stuck in place for days on end, leading to unusual warmth for folks under the ridge and an unseasonable chill for those beneath the upper-level low.

Modeled temperature anomalies on Thursday afternoon. | Source: Tropical Tidbits

Fortunately—though a little less so for folks who wanted to go to the beach for the long weekend—this pattern will start to diminish as the low weakens and broadens out, allowing the big ridge over New England and eastern Canada to dominate heading into the beginning of June.

Temperatures will start to rebound in the Mid-Atlantic and Carolinas by mid-week, and very warm temperatures will persist across the northern U.S. and much of Ontario and Quebec heading into the beginning of June.

[Satellite Image: NOAA]

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I graduated from the University of South Alabama in 2014 with a degree in political science and a minor in meteorology. I contribute to The Weather Network as a digital writer, and I've written for Forbes, the Washington Post's Capital Weather Gang, Popular Science, Mental Floss, and Gawker's The Vane. My latest book, The Skies Above, is now available. My first book, The Extreme Weather Survival Manual, arrived in October 2015.