June 6, 2021

Intense Heat Wave Shatters Records In Rarely-Roasted Parts Of U.S. And Canada

An intense heat wave that's swept over the United States and Canada over the last week will hear its last hurrah in New England and the Canadian Maritimes on Monday before temperatures cool down to a more manageable level. The heat set impressive temperature records from California to Manitoba, generating more heat than some communities have seen in a generation.

A strong upper-level ridge formed over the eastern Pacific early last week, bringing unseasonably hot temperatures to the West Coast. The high temperature in Sacramento, California, reached 105°F on Monday, May 31, the second-earliest instance of such a hot reading in the state capital. (The earliest temperature of 105°F or hotter in Sacramento occurred on May 28, 1984.)

Temperatures didn't get any cooler as the ridge crested the Rocky Mountains. The pattern allowed high temperatures to break the century mark as far north as Manitoba, which saw some of its hottest readings in decades.

Friday, June 4, saw a scorching high temperature of 106°F in North Dakota's capital of Bismarck, while Grand Forks, North Dakota, saw its first triple-digit reading since 1989. High heat continued moving east with the ridge, with temperatures well into the 90s across parts of Maine and eastern Canada.

It's not easy to get this much heat this early in the season. A strong upper-level ridge allowed the heat to crank as the feature crossed the United States and Canada. Weather conditions beneath an upper-level ridge are usually calm and warmer-than-normal because ridges foster sinking air, which heats up and dries out as it descends toward the surface. Southerly winds reinforced the warmth.

The powerful upper-level ridge had assistance from the drought plaguing the northern Plains and Canadian Prairies. The latest update of the U.S. Drought Monitor found extreme to exceptional drought covering much of the northern U.S. and south-central Canada.

Soil moisture and vibrant vegetation both add humidity to the air, which typically helps to modulate temperatures in agricultural communities during the heat of the summer. (Think about how humid it gets in places like Iowa and Illinois when the corn is in season.) Lacking that additional moisture, temperatures were able to climb far higher than normal, breaking longstanding records in many locations.

It'll be another hot day on Monday with high temperatures approaching the upper 90s in parts of New England and eastern Canada. The NWS's forecast on Sunday night called for a high of 98°F in Manchester, New Hampshire, on Monday afternoon, while highs could top out in the 90s on Prince Edward Island, where a heat warning is in effect. Temperatures will return closer to normal as the week wears on.

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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.