First 2025 heat warning issued in Canada. What does it mean for Maritime weather?

CTV Meteorologist Kalin Mitchell explains how the hot weather developed, how long it will last, and where it moves into next.

The first heat warnings of 2025 have been issued in southern Manitoba and parts of Northern Ontario, and while the Maritimes won’t get as hot, people can expect a jump in temperature later this week.

Heat warnings

Heat warnings have been in place for much of southern Manitoba going back to Saturday, including Winnipeg which reached a high of 31.5 C on Sunday with a high of near 34 C forecast for Monday.

The city remains under the heat warning, which advises that some high temperature near the mid-30s could persist though Wednesday. Numerous communities in southern Manitoba had record-setting high temperatures for a May 11 on Sunday.

A broad ridge in the jet stream – faster moving winds high in the atmosphere that play an important role in the weather pattern across the continent – has allowed for some heat to build up out of the southwestern U.S. straight into southern Manitoba and Northern Ontario.

The heat has been enough to create a critical fire danger rating in the U.S. Northern Plains and Upper Midwest. Much of the area under the heat warning in Canada is rated as being in extreme fire danger conditions.

The ridge of heat is broken by a stalled-out low-pressure system sitting over the U.S. Gulf States. That low is cycling some warm air out of the southeastern U.S. into parts of Southern Ontario. That ridge of very warm air will drift towards the Maritimes during the Wednesday-Thursday period of this week.

Maritime warm-up

The more easterly ridge of heat will move towards the Maritimes this week.

Northern and western areas of New Brunswick could reach high temperatures in the mid-20s on Wednesday with interior areas of western Nova Scotia in the low-to-mid 20s.

The ridge is more completely over the region on Thursday. High temperatures in New Brunswick could reach the mid-to-high 20s. Highs in Nova Scotia and Prince Edward Island could be in the low-to-mid 20s. There may be cooler areas directly on parts of the coastlines.

While very warm, even hot, for May, it is unlikely to trigger a heat warning for the Maritimes. Most of the daily high temperature records in the Maritimes for a May 14 range in the mid-to-high 20s with a few near 30 C.

I don’t think we will see widespread records matched or set on Thursday but a couple of areas could come close to their standing records. The record high for the Halifax area for a May 14 is a somewhat surprising 22.3 C at the airport and 19.9 C at Shearwater. That would be a spot that I could see setting a new record on Thursday.

What goes up, comes down

While I’m sure many would enjoy a few warmer May days, the climb in temperature isn’t expected to last all that long.

A weak weather front is expected to cross the Maritimes on Wednesday. That will increase cloudiness over the region and bring a chance of showers, cooling temperatures by a few degrees.

After that, low pressure and more widespread areas of rain and showers are expected Saturday, cooling temperatures further.