Canada's October temperatures set to teeter-totter due to record-breaking U.S. heat

A stand of prairie grass is silhouetted against the sun in this file photo. (Source: AP Photo/Michael Conroy)

Moving into the second week of October, the eastern half of Canada can expect some brisker fall air to break down from the north. At the same time, southern parts of the Prairies could see temperature rise well above seasonable as a ridge of heat builds in out of the southwestern United States.

Record-breaking heat in the U.S. Southwest

A stagnant area of high pressure has trapped increasingly hotter air in the U.S. Southwest. In meteorology, this is sometimes referred to as a “heat dome”.

Previous high temperature records for early October are being smashed in states such as Arizona and California. Palm Springs, CA, set a new record high temperature of 47.2 C and Phoenix, AZ, set a record of 45.0 C.

The record at Phoenix is an all-time high for an October and the latest into the year a temperature of 43 C or more has been recorded (it was previously Sept. 19), according to the National Weather Service. Approximately 39 million Americans were under a heat warning on Wednesday.

Further record-setting high temperatures are expected this week.

Temperature teeter-totter

Could Canada get into some of that U.S. heat? Next week there is a chance that southern parts of the Prairie provinces could experience a touch of “Aug-tober.”

A change in the jet stream – higher level winds that typically mark the border of areas of warm and colder air in the atmosphere – will see a ridge develop northward over the Canadian Prairies while a trough dips southward into eastern Canada.

Under the ridge a southerly wind will bring some of the very warm air in the U.S. Southwest northward. Some long-range forecast guidance indicates it may be enough to push high temperatures towards the mid-to-high 20s in parts of southern Alberta, Saskatchewan, and Manitoba Tuesday and Wednesday. Those high temperatures would be near 10 degrees above early October averages for that part of the country.

In the meantime, eastern parts of the country that enjoyed a mild start to October get a taste of cooler Autumn air. High temperatures in parts of Ontario, Quebec, and Atlantic Canada lowering into a range of the high-single digits to mid-teens. It should be noted that in many cases that level of temperature is seasonable to just a touch below for early October.

Early October heat records in Canada

There is a chance southern parts of the Prairies could approach standing daily high temperature records next week. That will depend on just how much of a push the warmer air in the U.S. gets northward. It has been plenty warm in early October in years past for the southern Prairies.

If we look at Oct. 9, the standing high temperature record for Winnipeg is 27.8 C, set in 1938. For Regina, Saskatchewan, it is 30.1 C, set in 1910. The record daily high temperature for Calgary is 25.4 C, which was set in 2023.

Despite the warm up, most long-range weather models indicate temperatures falling short of those standing records at this time.