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The relativity of the season


Being next to a large body of water has moderating effects on temperature and precipitation forecasts in Nova Scotia (courtesy: Jonathan Rhynold)
Being next to a large body of water has moderating effects on temperature and precipitation forecasts in Nova Scotia (courtesy: Jonathan Rhynold)

Gary Archibald, Weather Broadcaster, The Weather Network

March 20, 2013 — Depending on where you live in Canada, the spring season ushers in change on a varied scale.

Windchill into the -40s is not unheard of in Winnipeg (courtesy: Vince Pahkala)
Windchill into the -40s is not unheard of in Winnipeg (courtesy: Vince Pahkala)

Temperatures tend to rise, vegetation awakens from its winter slumber and you may have to shed a layer or two as you adjust to the seasonal metamorphosis.

I find it fascinating that one’s geographical location, including proximity to large bodies of water, mountain ranges or low-lying plateaus can dictate how the seasons will evolve. Knowing these geological features and the climatological trends associated with them will give a better sense of the weather scenarios that are likely to unfold.

Why do some cities with similar latitudinal co-ordinates, but different longitudinal ones, have different precipitation and temperature norms?

Let’s compare the climate norms for two Canadian cities: Winnipeg, Manitoba in the Prairies and Halifax, Nova Scotia in the Maritimes.

Nova Scotia experiences a “Maritime climate”. Being next to a large body of water -- the Atlantic Ocean -- has moderating effects on temperature and precipitation forecasts throughout the year.

In contrast, cities in the Prairies experience a climate driven by continental elements. Not having an ocean nearby changes things; in Winnipeg, temperatures are much warmer in the summer than the winter.

Maritimers, on the other hand, do not experience as cold a winter, but it can still be quite active due to Nor'easters and other types of storms.

You can see just how different the climates in these two cities are by comparing a climograph of Winnipeg with a climograph of Halifax.

On average, Halifax receives much more annual precipitation than Winnipeg.

Here’s why:

seasonal averages vary across the country (Karen Yuskin)
seasonal averages vary across the country (Karen Yuskin)

Cold Arctic/Polar air sinks south with the Polar jet, dropping temperatures across the Prairies and northern US central plains.

With cold air in place, clipper systems generate a fair amount of Prairie storms, as well as a few blizzards.

Windchill into the -40s is not unheard of in Winnipeg, but not likely in Halifax.

That’s because the ground cools down during the winter months quickly in the Prairies. In the summer it’s the opposite: the Prairies warm much quicker.

Winnipeggers experience a sharp incline as the temperatures warm from January to July. 

But in the Maritimes, water in the Atlantic is slow to heat up and slow to cool, meaning that the temperature climb is from the winter to summer is not as steep as the temperature trend is in the Prairies.

Spring, summer and autumn are collectively more active in Halifax, with a combination of all precipitations types, including snow, rain and ice pellets.

The general tendency for storms is to move from west to east across the continent, often with seasonal jet stream trajectories driving low pressure systems to the east.

Due to its location, the Maritimes will often see the tail-end of storms that gestate over the Colorado Rockies or the Texas Panhandle.

Do a search for a climograph for your city, or one that shares your latitude but differs in longitude – preferably a location with a much different geographical location to your own.

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