Weather in Ottawa in December

The month to avoid. December is the month most people should skip in Ottawa. Highs sit at -2.6 °C and the day is short; this is an indoors-with-excursions month, not an outdoors-all-day one.

December ranks 12 of 12 — near the bottom of Ottawa's year. September is the month that works, and the swing between the two is 64 points, which is a different holiday rather than a slightly better one.

This is persistent light rain rather than storms: 14 wet days but only 2 heavy ones. It rarely cancels anything outright, and it rarely fully clears either. A jacket beats an umbrella. Layers, and a genuinely waterproof outer — at -2.6 °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 17 °C and the coldest night fell to -34.9 °C, and the wettest single day dropped 33 mm — roughly 41% of the month's rain in one day.

December is statistically steady but not small: the year-to-year variation is modest in relative terms, yet the wettest December on record still delivered 119 mm against 26 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 80 mm average is a reasonable planning figure, not a promise.

Wind is light at 2.5 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 92%, which at -2.6 °C means damp rather than muggy — the kind of cold that gets into a coat and stays there.

How December sits in the year

The month is on the way down: 8.2 °C cooler than November, with January dropping another 3.9 °C. The first week and the last are not the same trip.

Daylight in December

December sits at the dark end of Ottawa's year — 8.8 hours of daylight against 15.6 at midsummer, holding steady all month. Sightseeing days are genuinely shorter, and an itinerary built for summer will not fit.

An inland climate

Ottawa has no sea to moderate it, and it shows: 42.4 °C separates the hottest afternoon of the year from the coldest night. That is a genuinely continental range, and it means summer and winter here are barely the same place.

How busy it gets

Off season. The genuine off season: cheapest by a distance, with the caveat that some tours and restaurants close entirely.

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

December in Ottawa versus nearby

If Ottawa is one option among several, the nearby comparison is worth making. Kingston is close enough to be a coin toss — 4.6 °C warmer, 4 days more rain. Montréal is close enough to be a coin toss — within a degree on temperature, 1 day more rain.

So: December is a compromise. September is 64 points better and is what Ottawa 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 Ottawa

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