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OTTAWA | Coldest snowstorm

Coldest Ottawa snowstorm in more than 100 years

Caroline Floyd

Monday, January 21, 2019, 7:30 AM - Ottawa earned some dubious distinctions when it comes to winter weather this past weekend. First, Ottawa residents awoke Saturday morning to find themselves living in the coldest capital city on Earth, clocking in about 20 degrees colder than winter heavyweights like Moscow and Helsinki, and even edging out perpetual champ Ulan Bator, Mongolia, by a degree.

That morning low of -24°C combined with nearly 30 cm of snow reported at Ottawa Airport, set the city up to chalk up another unusual milestone this weekend -- the coldest snowstorm in more than 100 years.

(Related: Winter blast, extreme cold grip Ontario)

Cold and snowstorms do typically go hand in hand, and while it can't actually be 'too cold to snow'*, heavy snow is much harder to generate the lower the temperature drops. By the time you get into the -20s and -30s Celsius, heavy snow is fairly uncommon, but that's not because it's too cold; rather, it's because the air is too dry. The amount of water vapour the air can hold decreases as the temperature goes down; so the colder it gets, the less moisture there is available to make snow. That's also why you tend to see smaller snowflakes in colder weather, rather than big clumpy ones.

As daytime highs struggled to climb out of the minus 20s over the weekend, Ottawa saw one of the coldest days with significant snowfall since 1895. On Saturday, the daytime HIGH reached -19.3°C, with a low of -24.2°C, but less than 5 cm of snow fell. Sunday was the big snow making day with over 20 cm recorded in the city. Combine that with a daytime high of -17.4°C and January 20, 2019 ranked as the coldest snow storm to hit the city in over 100 years. The intense cold, which collided with a healthy stream of moisture direct from the mild Gulf of Mexico is to blame for this rare occurrence and Ottawa just happened to find itself at the intersection of the two.

While the snow has pushed out of the region, the cold will linger into the new week, with wind chills in the -20s hanging on into the start of the new work-week. It caused several school bus cancellations in the Ottawa area early Monday. A gradual climb back toward seasonal follows for the rest of the week, but don't let your guard down -- another cold blast is on the horizon for next weekend.

*Okay, actually it probably can be too cold to snow. At absolute zero, a.k.a. 0 Kelvin or -273ºC, it is fair to say it probably wouldn't snow. But if that's the temperature outside, you're going to have much bigger problems than accumulating snowfall.


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