Summer of 2012 will feature above-normal warmth for much of Canada, while more thunderstorms than usual target eastern Ontario and southern Quebec. Nova Scotia and Newfoundland will be more susceptible than normal to tropical system impact later in the summer.
There will be widespread above-normal warmth across much of the nation, especially across the southern Prairies. Extended spells of heat are anticipated to grip the southern Prairies.
It will be hot for Calgary and Edmonton with below-normal rainfall.
A dome of high pressure will be set up across the central Plains of the U.S. early in the season. It will build northward and westward across the Rockies as the summer progresses, promoting the hot and dry weather across the Prairies.
An exception to the widespread warmth will be an area from Windsor, Ontario, to Montreal, Quebec. In this zone, any prolonged heat spells will be few and far between. Instead, near-normal temperatures are expected.
Active, stormy weather will occur across eastern Ontario and southern Quebec, keeping long heat spells at bay. Cities that lie in the path of more stormy weather this summer include Ottawa, Ontario, and Montreal and Quebec City, Quebec.
"There will be cooler air aloft this summer, making the atmosphere more unstable and conducive for thunderstorm development," said Expert Senior Meteorologist Brett Anderson.
Meanwhile, there is an increased tropical storm threat for Nova Scotia and Newfoundland later this summer, since steering currents in the tropics may be directed toward Atlantic Canada.
When making a long-range forecast, meteorologists look back at analogue years where there was a similar pattern to help make the forecast. Anderson explained that the summer of 2006 was one of the analogue years analyzed for looking at potential tropical impact.
In 2006, a total of four weakening tropical systems had some impact on Atlantic Canada. There was a transitioning pattern toward an El Niño during the summer of 2006 similar to how AccuWeather.com Long-Range Forecasters expect the pattern to be in transition this summer.
"A lot of years that are transitioning into El Niño have seen tropical systems approach Nova Scotia and Newfoundland," Anderson added.
It will also be a warmer and more humid summer than usual with above-normal rainfall for eastern parts of Atlantic Canada.
St. John's, Newfoundland, is among the cities forecast to have above-normal rainfall for the summer. There will be more cloudy and foggy days compared to normal.
Meanwhile, in western Canada, it will be a pleasant summer for outdoor activities in British Columbia, including in the Canadian Rockies.
Temperatures and precipitation will be near-normal for Vancouver.
After an earthquake hit in the area, the Bardarbunga volcano erupted Friday in Iceland, causing a temporary no-fly order.
The North Central states face the most adverse weather this Labor Day weekend, in the form of severe storms and tornadoes which will threaten lives and travelers.
As Cristobal loses its tropical characteristics, attention is turning toward the Bay of Campeche for potential development next week.
The Pittsburgh area will have a turbulent stretch of sun and intermittent thunderstorms for the next several days, including storms that could impact Labor Day weekend plans.
An outbreak of severe weather, including tornadoes, will evolve on Sunday from the northern and central Plains to part of the Upper Midwest.
After another big cooldown, warm and humid weather will bounce back in Boston, during the Labor Day weekend.
Pittsburgh, PA (1982)
39 degrees, coldest ever in August.
Anchorage, AK (1989)
A total of 9.6 inches of rain -- wettest August on record.
New England (1816)
"Year in which there was no summer", otherwise known to weather historians as "1800 and frozen to death" killing frost once again damages sparse corn corp in northern New England...loss of this and other crops led to severe famine in much of New England that winter...and helped spur western migration in spring of 1817.