Weather in Calgary in December

The month to avoid. Of the twelve, December is the one to avoid. Highs sit at -1.7 °C and the day is short; this is an indoors-with-excursions month, not an outdoors-all-day one.

December ranks 11 of 12 — near the bottom of Calgary's year. August is the month that works, and the swing between the two is 55 points, which is a different holiday rather than a slightly better one.

Rain falls on only 5 days, so an itinerary with no wet-weather fallback is a reasonable risk. Layers, and a genuinely waterproof outer — at -1.7 °C the difference between a good day and a miserable one is entirely down to what you are wearing.

What the averages hide

Averages flatten a month, and this one hides a few things: 30 nights drop below freezing, so anything left outside stays frozen. Across the twenty years measured, the hottest December day reached 11.3 °C and the coldest night fell to -32.5 °C.

December is moderately variable: 5 mm in the driest year against 49 mm in the wettest, around an average of 21 mm. Roughly two Decembers in three land near that average, and the third does something else entirely.

Wind is light at 5.8 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 82%, which at -1.7 °C means damp rather than muggy — the kind of cold that gets into a coat and stays there.

How December sits in the year

Temperatures hold steady either side: 3.5 °C in November, -1.7 here, -1 in January. Nothing about the timing within the month matters much.

Daylight in December

December sits at the dark end of Calgary's year — 8 hours of daylight against 16.5 at midsummer, losing 0.4 hours across the month. Sightseeing days are genuinely shorter, and an itinerary built for summer will not fit.

An inland climate

With no coast nearby, the year swings a fair way — 35 °C between the warmest afternoons and the coldest nights, wider than any coastal city at this latitude would manage. At 1048 m the air is thin enough to matter — sun that burns faster than the temperature suggests, and nights that cool off quickly.

How busy it gets

Quiet. Few other visitors, cheaper rooms, and a real chance some seasonal operators are shut.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

December in Calgary versus nearby

If Calgary is one option among several, the nearby comparison is worth making. Banff is the weaker option in December — 4.4 °C cooler, 9 days more rain. Lethbridge is close enough to be a coin toss — within a degree on temperature, 3 days more rain.

So: December is a compromise. August is 53 points better and is what Calgary is actually like at its best — worth moving the trip for if that is possible, and worth adjusting expectations for if it is not.

Every month in Calgary

See all twelve months in Calgary, or where else to go in December.