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Ulf T. Runesson

Faculty of Natural
Resources Management,
Lakehead University

955 Oliver Road,
Thunder Bay, Ontario,
Canada P7B 5E1

     (807) 343-8784

     (807) 346-7769


Northwestern Ontario covers a huge area. Superimposed on Europe, it would extend from Paris and Munich in the south to Scotland and Denmark in the north. It would encompass several countries, including Denmark, Holland, Belgium, Luxembourg, Germany and Austria. Given this vast area it's no surprise there are weather extremes and different climates.

Located near the centre of North America most of the region has a continental climate with warm to hot summers and cold winters. Spring and autumn tend to be short seasons sandwiched between and have some of the weather of winter and summer. Lake Superior moderates some of the temperature extremes and some of the large lakes in the region add to winter snowfall and subtract from summer rain on a local basis.

The annual temperature (the average of all temperatures during the year) varies from 2 or 3 degrees Celsius (°C) in the south to about -4 °C in the far north.

Several locations share the record maximum temperature for Ontario of 42.2 °C Atikokan, Fort Frances (and Biscotasing in Northeastern Ontario). Many stations in the south have recorded all time maximums of 40 °C and occasional days of 35 or more are not uncommon.

At the other end of the thermometer are places like Central Patricia, Hornepayne, White River and Geraldton with all time minimums lower than -50 °C. White River, in spite of claims of being the coldest place in Canada (this honour belongs to Snag in the Yukon) is not even the coldest in Ontario - Iroquois Falls at -58.3 °C has that record.

Precipitation is highly variable both year to year and location to location. As a generalization precipitation increases as one moves from the northwest to the southeast. For example, an average of 600 millimetres (mm) of precipitation falls per year in the Big Trout Lake area. To the southeast the total is around 900 mm Marathon/White River area. In Thunder Bay the annual average is just over 700 mm. The bulk of the yearly total occurs in the summer months - May to September - with showers and thunderstorms.

The growing season is also in these months and periods of extended drought are uncommon.

The winter of 1995-96 broke a period of overall decline in winter snowfall amounts. People who recall winters with more snow in the 1950s and 60s are correct, although part of this memory may be as children looking up at massive snow banks. The record snow season for Thunder Bay and vicinity is 1955-56 with 430 cm or 14 feet. The above record by comparison is not too remarkable. In an average winter Searchmount, to the east of Lake Superior, receives the same -- 430 cm. There are snow belts scattered throughout the region. Some are because of upslope terrain and some because winds pass over open water. Some, like Searchmount, have both.

The winter of 1995-96, with 355 cm at Thunder Bay, claimed second place. Much of the region had an extended snow season with amounts well above normal The current winter is more difficult to summarize because it varies from normal or below normal at some locations near Lake Superior to much more than normal in the west.

The record five day snowfall in Ontario belongs to Nolalu, west of Thunder Bay, with a massive 198 cm which fell during the 4th to the 8th of December, 1978.

Thunder Bay is the sunniest location in Ontario and, for that matter, the whole of eastern Canada with just over 2200 hours of bright sunshine. Sunshine totals in the region tend to decline to the north and the east.

The prevailing winds in the region tend to have a westerly component although local terrain may deflect the winds somewhat. Annual wind speeds are not high when compared to other regions in Canada. All time record wind gusts barely exceed 100 km per hour and some locations like Big Trout Lake, Armstrong and White River have not reached this threshold. In part this is due to the landscape and the forests which provide friction. On Lake Superior winds exceeding 100kmh are uncommon but not too remarkable especially in the "gales of November".

Vehicle accidents and fatalities caused by winter weather are a danger because of slippery road conditions caused by snow and freezing precipitation. Freezing rain or drizzle is not as common as in Southern Ontario but still is an occasional hazard throughout the region.

Extreme cold temperatures are often during times of high pressure which typically has light winds but when cold and brisk winds combine, the result can be extreme wind chill values.

The Environment Canada use of the term "Severe weather" refers to weather associated with thunderstorms or hurricanes. Hurricanes in their late stages can cause havoc in Atlantic Canada and very occasionally in Southern Ontario (Hurricane Hazel being the most notorious example) but are a non event in Northwestern Ontario.

Place names containing "Thunder" (Thunder Bay, Thunder Lake, Thunder Cape) suggest that thunderstorms are not unusual in the region. Annual totals are in excess of 30 in the extreme south (Fort Frances, Atikokan). The numbers gradually decline to the north. Almost all thunderstorms occur April to October and are concentrated in June, July and August but occasionally thunder can be heard during a snow storm.

Thunder in itself may frighten but does not cause damage. Lightning does. Most of the forest fire starts in Northwestern Ontario are caused by lightning. Occasional human fatalities happen with lightning strikes. Hail is uncommon but, on occasion, is present during severe thunderstorms. Tornadoes are also associated with thunderstorms but are quite rare in the region. There are occasional sightings.

The Fort Frances area, an extension of the Prairies, seems the most prone to extreme severe weather. A hail storm during the summer of 1996 caused considerable crop and property damage.

The length of the growing season is related to local topography. Frost can occur at one site, but at another nearby location the temperature remains above freezing. Temperature declines with altitude and Raith, located on a height of land, has a very short growing season. On clear still nights cold air collects in hollows which are typically frost prone.

In the southwest - Kenora to Fort Frances - the average frost free period begins in late May, in Thunder Bay on May 31st. In the far north the date is several weeks later. In the fall the first frost occurs in early to mid-September in the south and in late August in the north. These are averages and frost frequently occurs in June and August. Again, depending on the local terrain, it is possible to have ground frost in July. This kind of frost is usually light and not prolonged. Most crops and vegetables can survive this kind of event.

Last Modified: January 20, 2014 20:01:06. 
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