Weather: North America
North Americas mercurial climate has something for everyone. Severe hurricanes, killer tornadoes, crippling snowstorms, torrential downpours, withering drought and a fair share of nice weather, too – all pay frequent visits to this prosperous, yet vulnerable, land that stretches from the Canadian Arctic to tropical Mexico. Hollywood has bombarded the world with films of extraordinary American weather, painting a picture of the continent as one big meteorological melodrama. In reality, most short-term visitors will experience nothing more ominous than a few brisk wind shifts, some bursts of rain or snow, and perhaps a thunderstorm. Moreover, because North America – especially the United States – is so weather-obsessed and media-saturated, you're likely to hear if any truly threatening weather is in the offing.
The main reason for the frequent and dramatic changes in North America's weather is the region's unique geography. Most continents have mountain ranges arranged in a variety of orientations, but only the Americas have substantial north-south ranges that run the entire length of both continents. This barrier tends to block marine air flowing in from the Pacific on the westerly winds that encircle the globe at mid-latitudes. Within North America, only the west coasts of the US and Canada have climates akin to the more muted regimes of Europe, where Atlantic air dominates.
With the Pacific influence so restricted, you might expect the rest of North America to be a parched and barren domain, like the Australian Outback. Actually, the eastern half of the US and Canada is by and large a fairly moist place. Forests cover a good deal of the landscape outside cities, and almost every spot in the eastern US gets more rain than London, Beijing or Cape Town. The sub-tropical Gulf of Mexico is in a perfect position to moisten southerly winds that feed into storms sweeping across the US and southern Canada. And the western Atlantic is warmed by the north-flowing Gulf Stream. This allows coastal storms – even in winter – to tap into a source of near-tropical warmth well into the mid-latitudes.
It's a good 4800km/3000 miles across Canada from Vancouver to Halifax. Much of that trek is across glacier-levelled prairie and woodland. The great flatlands that stretch from central Canada south to the Gulf coast are a super- highway for bitter Arctic northerlies that pour down cold air each winter. In the summer, the traffic flow reverses, and southerly winds scream north, carrying warmth and moisture (the US state of Kansas is named after the indigenous Kanza tribe, the “people of the south wind”). When these competing air masses fight it out, especially in the spring, intense thunderstorms and tornadoes often result
The western mountains of North America spill across Mexico's western half, with a vast plateau extending to the east. The high terrain mixes with the low latitude to produce a pleasing combination of ample sunshine and warm temperatures that rarely reach scorching levels, except in the extreme northwest. Rainfall tends to be focused during the six-month wet season, from about May to October, when most of Mexico falls under the influence of tropical trade winds. Hurricanes can boost the rainfall total and wreak havoc along the south and east Mexican coastlines – as well as along the US east coast from Texas all the way to New England.
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