September 2012 Continues a 15 Month Trend

September quick stats - click to enlarge

Drought-like conditions dominated

     September continued a trend 15 months in the making. The month averaged warmer and drier than normal. Drought-like conditions plagued not only us here, but also most of western Canada throughout the month. Here in Winnipeg, only 4.0 mm of rain fell, just 8% of normal putting September 2012 as the second driest on record. It was the 4th consecutive drier than normal month. It also makes it the 37th driest month in history. That may not seem like something of interest at first, until you consider that there are 1678 months of precipitation data.

Top 5 driest Septembers:
1.    1.3 mm    1948
2.    4.0 mm    2012
3.    6.1 mm    1938
4.    8.6 mm    1897
5.    9.9 mm    1976

     Another interesting note about September was the large diurnal temperature variations. While daily highs averaged 1.9°C above normal, daily lows averaged 1.3°C below normal and tied for 21st coldest. The average difference between day and night was 15.8 degrees when normally it is just 12.6 degrees.

     As a result, both record highs and record lows were seen. The month started hot with highs in the mid to high twenties, but then things began to change mid month. The growing season officially ended September 14, a week earlier than normal. But then even colder weather dominated the third week with several days of below zero overnight lows. Snow even fell in parts of northwestern Ontario. The morning of the 23rd was enough to be considered ''frigid'' to many as temperatures dipped well below the freezing mark. Winnipeg dipped to -7.1°C, making it the 5th coldest September night on record. It was also the coldest September night in 47 years. The coldest spot in the area was Dugald at -9°C.

     In total, 7 days had lows below zero during the month, tying for 3rd most on record for the month. The following is a diagram demonstrating the frequency of below zero nights in September since 1872, showing that the amount of below zero nights this September was in fact unusual:

      Only a week later, record daytime highs became the headline. Temperatures approached 30°C on the 29th and reached the low to mid twenties on the 28th and 30th. The hot and sunny weekend coinceded nicely with the peak of the colour change of the leaves, pehaps making it one of the nicest Fall weekends in a while.