A chinookis a warm, dry wind that arrives from the west after crossing the Rocky Mountains, and it is the reason Calgary's winter temperatures are so volatile. On a chinook day the high can run 13 to 25 °C above normal, turning a deep freeze into a melt and back again within the same week, and the Canadian Encyclopedia records a rise of 27 °C in two minutes at the start of one. The chinook belt lies almost entirely within southern and central Alberta, and in the southwest of the province about one winter day in three is a chinook day.
Air moving in off the Pacific is forced up the western slope of the Rockies. As it rises it cools, and it drops most of its moisture as rain or snow on the British Columbia side. Having lost that moisture, it is a much drier parcel of air by the time it crests the divide — and dry air warms faster on the way down than moist air cools on the way up. It arrives on the Alberta side compressed and considerably warmer than it started.
The visual signature is the chinook arch: a long band of cloud along the western horizon with a strip of clear sky beneath it. If you can see the arch from Calgary, the warm-up is usually already on its way.
The west side leads. Higher, more exposed districts like Signal Hill — and Cochrane further west, where the Bow valley opens out of the foothills — register the warmth and the wind before the rest of the region. East Calgary is typically last, and on a strong chinook afternoon the temperature difference across the city can be several degrees. That gap is one of the clearest cases for a per-neighbourhood forecast rather than a city-wide one.
Chinooks are not purely good news. The wind is the main complaint — gusts strong enough to make driving on exposed routes unpleasant and to take down fences and shingles. The rapid thaw-and-refreeze cycle turns melted snow into sheet ice on sidewalks and side streets overnight, which is a bigger injury risk than the cold was. Many people also report headaches during the sharp pressure change, often called a "chinook headache". University of Calgary headache researchers found migraine attacks somewhat more likely on chinook days and the day before one, though the cause is still unproven.
For gardeners and homeowners, the repeated freeze-thaw is harder on plants and on concrete than a steady cold winter would be.
Watch for the arch on the western horizon, a sharp rise in wind from the west or southwest, and a falling then rapidly rising temperature. On this site, the quickest tell is comparing the west-side districts against the east side on the live map — when Cochrane and Signal Hill run well ahead of Forest Lawn, a chinook is working its way across the city.
To see whether one is on the way, the Calgary chinook forecast checks the next seven days of the model forecast for the chinook signature — a strong west or southwest wind arriving with a sharp jump in temperature and a drop in humidity. For the official forecast and any wind warnings, check Environment Canada's Calgary forecast.
A warm, dry wind that descends the eastern slopes of the Rockies, able to raise Calgary temperatures by 10–20 degrees within hours, and sometimes more than 20 over a day, most dramatically in winter.
The west and the higher west-side districts — when Cochrane and Signal Hill run well ahead of Forest Lawn on the map, a chinook is working its way across the city.
Look for the chinook arch — a band of cloud along the western horizon with clear sky beneath it — and a strengthening west or southwest wind. In a forecast, the signature is that wind arriving with a sharp temperature rise and falling humidity.