Sunday, 30 December 2012

#10 - Top Ten Weather Events of 2012 in the Winnipeg Area

Cold September Nights

     Although daytime temperatures were only a few degrees below normal in Winnipeg on the coldest days in mid September, they fell quite rapidly at night. On a few days, the difference in temperature between night and day was more than 20 degrees! This may have been thanks to very dry soil conditions which helped accelerate heat loss from the ground at night.

     The growing season at the airport ended on September 14 with a low of -1.0°C, about a week earlier than normal (Sep 22). This puts the length of the 2012 growing season at 106 days, shorter than the normal of 121 days. Of note however, this value for 2012 is a little misleading considering the ideal growing conditions seen this year due to a very warm Spring. By using the number of days between hard frosts instead (hard frost is defined as a night of -2°C and colder) we get a season of 148 days for 2012 (Apr 27 to Sep 21 inclusively). That is much more representative of the conditions experienced this year.

Snow in Kenora Sep 21
     The coldest weather of the month moved in a week later. Snowflakes fell in northwestern Ontario and areas north of Winnipeg on the 21st (video of snow in Kenora). Here in Winnipeg, heavy hail fell in some parts of the city midday with the passage of a cold front. Behind this disturbance, an arctic airmass under a ridge of high pressure allowed for record low temperatures on September 23. A low of -7.1°C was recorded at the Winnipeg airport, breaking the 133 year old record of -6.1°C back in 1879. It was also the coldest September night in 47 years (-7.2°C on Sep 26, 1965), the 5th coldest September night ever and the second earliest of its kind for the season. Even The Forks dipped to the freezing mark (0.0°C) marking the end of the growing season for dowtown, about 2 weeks earlier than normal (Oct 5).

     The cold spots were Dugald at -9°C and Emerson and Fisher Branch at -8.5°C. Some official record low temperatures across the province included:

     Despite such a chilly start to the day, temperatures skyrocketed through the day with daytime highs in the high teens, seasonal for that time of year. Winnipeg reached a high of 17.2°C, a 24 degree rise from what it was early that morning!

     In total, 7 days had a low below zero in Winnipeg, tying for third most subfreezing days on record for September. Click here for a graph demonstrating the frequency of days with a subfreezing low in September since 1872.

This post contains pictures, videos or information from the following sources

The Weather Network
Environment Canada Weatheroffice

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