The Summer Season: Weather Contrasts and some Heat Warmings

Warmer than average temperatures prevailed across Northern Ontario in early June. For gardeners in the Northwest this warmth was accompanied by generous rain amounts, hence a good beginning to the growing season. However, a much cooler air mass moved into the region in the second week. Widespread frost was experienced in northern communities and morning temperatures just above the freezing point were common in locations like Fort Frances, Sioux Lookout, Dryden and Thunder Bay on June 10th and 11th. Gardeners that pay attention to weather forecasts and/or are able to “read” weather conditions themselves probably covered their plants. Most avoided serious frost damage.

This very cool air did shift eastward and seasonal temperatures persisted for the rest of June in the Northwest.

Last month, in the middle of June, I was startled how quickly Environment Canada’s severe weather warnings went from concerns about frost to warnings about potentially dangerous heat in Northeastern Ontario. Three or four days seems a short duration to go from record low temperatures and frost in many locations to temperatures of 30° C and higher. I was focusing on an area in the Northeast from Moosonee, Kirkland Lake and Timmins and south to Highway 17, (Sault Ste Marie, Sudbury and North Bay). Morning temperatures on June 15 were below freezing in many northern communities and just above 0° C in more southerly areas. (Yes, it seemed to be a repeat of what had happened a few days earlier in the Northwest.)

By June 18, afternoon temperatures were generally above 30° C in Northeastern Ontario. This was the northern extension of a significant heat wave that was affecting all of southern Ontario and most of eastern North America. A few daily temperature records were set in the Northeast. Most remarkable was the humidity that penetrated far into the region. The Humidex reached 45 in Chapleau on June18th (Toronto reached 44 on June 19th). Extreme Humidex readings of 35 to 40 were recorded from Moosonee to Sudbury.

I was curious about how these “feel like temperatures” compared to the Deep South. Chapleau and Moosonee were a bit more uncomfortable than Atlanta, Georgia throughout the afternoon on June 18th.

Another heat wave took place later in June in Northeastern Ontario. Most communities experienced several days with temperatures warmer than 30° C. This contrasted with what happened in the Northwest where a temperature of 30° C was rare. The warmest temperature for Fort Frances, Atikokan and Thunder Bay was 29° C. Oddly, Peawanuck and Kitchenuhmaykoosib Inninuwug (KI or Big Trout Lake), about 600 kilometers north of Thunder Bay, did exceed the 30°C threshold in June.

One more weather oddity from the far north - on July 1st Attawapiskat and other First Nation communities next to Hudson Bay, took turns for being the warmest locations in Ontario and, occasionally in the morning hours, the warmest places in Canada. They were in an eastern extension of a heat dome situated over northern Manitoba.

Heat wave or heat dome?

The high temperatures in mid-June revised a debate in Canada about what to call extended times of hot weather. “Heat wave” is commonly defined in dictionaries. The term “heat dome”, although not brand new, was commonly used during the remarkable June 2021 heat event over British Columbia, Washington and Oregon. The B.C. provincial coroner's service linked more than 600 deaths to the extreme heat, and temperatures warmer than 40° C were common in the BC interior.

The terms “heat dome” and “heat wave” do not appear in Environment Canada's glossary of weather terms.

David Phillips, a senior climatologist at Environment Canada, defines a heat dome as a stationary high-pressure area that covers a bigger area, doesn't cool down at night and is potentially more deadly. Phillips said he uses the term heat dome because it is "descriptive" and easy for the public to understand but he has noted some of his colleagues may not agree.

Whatever term we use, heat event, wave or dome, these higher temperatures experienced this June were somewhat unusual. It was relatively early In the season and, as well, featured ground level smoke from wildfires burning in British Columbia and Alberta.

Summer Solstice

The word “solstice” - from the Latin words sol (sun) and sistere (to stand still) - flags times when the Sun appears to stand still. For more than a week the hours of daylight, and times of sunrise and sunset, are almost identical. This year the Summer Solstice occurred on Thursday, June 20, for the Northern Hemisphere. The exact date shifts slightly each year because the calendar year does not match exactly the time it takes the Earth to orbit the Sun. The solstice always occurs between June 20 and 22, but during a leap year (like this year) it happens on June 20.

The Summer Solstice is often tagged as the first day of summer. Just because there is more daylight and the sun is at his highest point above the horizon, it does not mean, necessarily, that it will be hot. This year’s afternoon temperatures were close to seasonal and were followed by a return to cooler than normal temperatures that persisted until the end of June.

Outlook for July and August

So far in July, temperatures have been above normal by about 2°C across the region. Most locations inland from Lakes Superior and Huron have experienced 30° C and warmer. This is not surprising. Typically, July is the warmest month of the year and on average, the warmest temperatures happen in the 3rd or 4th week. All the major forecasting agencies are predicting above normal temperatures well into August.

A prediction: More heat warnings issued by Environment Canada are likely in the next few weeks.