After subjecting southern MB to 9 months of below normal temperatures, Mother Nature relented in dramatic fashion by delivering the warmest September on record across much of the southern Prairies. In Winnipeg, the month finished with an average temperature of 17.7C at YWG airport, over 5 degrees above the normal 12.3C and the warmest September in Winnipeg since records began in 1872. The month was nearly a full degree warmer than the previous warmest September of 1948 at 16.8C. In fact, September 2009 had a monthly mean of 19.0C through the 26th, before 4 days of cool weather at the end of the month shaved over a degree off the final average.
September 2009 was a summer-like month with plenty of sunny warm days, and only 4 days with measurable rain. The stretch between the 13th and 25th was especially nice, dominated by sunshine and 25-30C temperatures that was interrupted only one day with cloudy skies and a brief shower over the two week period. The month finished with an average temperature higher than any month of the year, the first and only time in Winnipeg’s climate history that September was the warmest month of the year. Every day from the 1st to the 27th was above normal with 19 of those days reaching a temperature of 25C or higher, the most 25C days of any September (previous record 16 days in 1940) and nearly twice as many as July had (10 days) Amazingly, no daily record highs were established during the month, highlighting the fact that it was the persistence of the warm weather that was the story, rather than any extreme heat. This was evident with the night-time lows, with no lows below 10C until the 22nd. A cool snap at the end of the month produced the season’s first frost on the 29th with a low of -2.4C at Winnipeg airport. Downtown however remained frost free all month.
Precipitation at the airport totaled 22 mm, less than half the average September monthly precipitation of 58 mm. Of the 22mm total, only 1 mm fell after the 11th. The sunny dry warm weather was a blessing for area farmers who needed an extended period of warm dry weather to make up for a slow growing season delayed by cool temperatures and rainfall. As a result, many crops were able to mature before the late frost, and be harvested in fine sunny conditions. The weather was also a boon to local beaches and golf courses, making up for some lost ground from a cool wet summer.
Overall, a September to remember! (see NCDC September summary for more info)