Spectacular September salvages sorry summer - September 2009 warmest on record

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)

2009 growing season ends for most of southern Manitoba

Clear skies and a light wind allowed temperatures to drop to below freezing this morning across much of southern MB, officially ending the 2009 growing season. The exception was near Lake Winnipeg and western MB where clouds kept temperatures above freezing overnight (see map) At Winnipeg airport, the temperature dropped to a low of -2.4C, ending a 114 day growing season that began late due to a record freeze on June 6th.

At Winnipeg airport, the average date of the first fall frost is Sept 22nd so today's frost was a week later than "normal", although the first fall frost date varies quite a bit from year to year. Average date for the last frost in spring is May 23rd which gives an average growing season of about 121 days using airport data. Last year, the airport had a 116 day growing season (Jun 3rd - Sept 26th), virtually the same as this year.

Within the city of Winnipeg however, frost was not widespread this morning. The Forks downtown had a low of +1.4C, and in Charleswood, my station registered a low of +0.5C with just some some light frost noted. Downtown Winnipeg has a much longer growing season than the airport, due to the urban heat island effect that keeps night time temperatures warmer than rural areas. The average first fall frost downtown is Oct 5th, while the last spring frost is May 4th giving an average growing season of 159 days downtown, or 38 days longer than the airport. For most areas of the city, the length of the growing season lies somewhere between downtown and airport values.

Chilly today.. frosty tonight...

No, that's not a Wendy's menu order.. that's the weather forecast for Winnipeg and southern Manitoba for the next 24 hours as a northerly flow of cool air spreads over the province. Gusty north winds today will keep temperatures only in the 12c range this afternoon, with cloudy skies and occasional sprinkles or drizzle from weakening off lake streamers. For tonight, high pressure will be building over southern MB, bringing clearing skies and diminishing winds.. perfect conditions for frost formation overnight. In fact, much of southern MB will see its first frost of the season by Tuesday morning with overnight lows of zero to -3C expected. The exception will be areas near and to the west of the MB lakes which will be saved from frost by the warm lake waters. Patchy cloud cover will also save some localities from frost tonight. Tuesday looks like a nice day with sunshine mixing with a few clouds, lighter winds, and afternoon temperatures of 12-15C.

Strong winds to bring cool change for Sunday.. gales, high waves for MB lakes Sunday night

The extended summerlike pattern of September 2009 will come to an abrupt end Sunday as a storm system tracks across Manitoba and intensifies over northwest Ontario Sunday night. Strong northwest winds on the backside of this system will draw in much cooler air over southern MB Sunday into Sunday night, with gusts of 70 to 80 km/h likely by Sunday evening over much of southern MB, with 90-100 km/h gusts possible on the eastern shores of Lakes Winnipeg and Manitoba. These strong winds will combine with high lake levels to create large waves.. possibly 3-4 metres high, which may cause problems along the exposed eastern shorelines of the lakes. In addition, the strong winds may result in tree limb damage and local power outages since most trees are still full of leaves thanks to a warm frost-free September. A similar storm system on June 27th brought 100 km/h gusts over southern Lake Winnipeg and resulted in extensive power outages through cottage country into the Whiteshell due to fallen tree limbs and power lines.

September sets new heat record... big cooldown expected Sunday

The summer-like weather of September 2009 will be one for the record books. With a maximum temperature of 26C Wednesday, Winnipeg registered its 17th day in September with temperatures of 25C or higher. This eclipses the previous September record of sixteen 25C days set back in 1940. And it looks like we'll add a couple more to the total before the week is through as temperatures of 25C or more are forecast both Thursday and Friday. This is in stark contrast to a very cool July, the 5th coolest on record, in which Winnipeg saw only ten days of 25C or more. In fact, September 2009 will finish with an average temperature greater than July, the first time that has ever happened in Winnipeg since records began in 1872.

The warm weather has been persistent for the past 3 weeks over southern MB with every day this month above normal so far. But changes are on the way. A storm system is expected to cross southern MB Sunday, which will draw in much cooler air Sunday into Monday on strong northwest winds. This will bring the first spell of below normal temperatures in over 3 weeks, with the risk of a widespread frost by Tuesday morning. The cool outbreak however should not be enough to offset this September finishing as the warmest September on record in Winnipeg as well as most of southern MB.