A cold night is ahead tonight for Manitoba and northwestern Ontario as the core of the arctic air moves over us as seen in the model image below. The coldest air is expected to be in eastern Manitoba and norhwestern Ontario where lows in the -30's are pretty much a guarantee.
I think Winnipeg has a very good shot at hitting -30°C tonight as well. It got down to about -29°C last night in the city and with even colder air aloft moving in tonight, I think it would be a miracle if we managed to escape -30°C once again. This would be the first -30°C reading since February 2011 in the city. In fact today marks the 395th consecutive day without hitting -30°C (if we don't hit -30°C this evening before midnight). The longest streak of days without -30°C was 714 days between Feb 15, 1930 and Jan 29, 1932.
Even if we don't hit -30°C tonight, we will have multiple chances to do so throughout the week as cold air sticks in place. With daytime highs in the minus twenties throughout the week, we may not reach the minus teens until the weekend.
In addition, wind chills warnings have been issued for all of southern Manitoba for tonight. Wind chills between -40 and -45 are likely tonight and tomorrow morning. This is a time for me to remind everyone that the wind chill is not a temperature. Read my explanation on what the wind chill value means here.
As I refered to a few lines earlier, we wont see any type of warmup until the weekend. And even that is expected to be brief as we are expected to return into the arctic air next week.