Monday, October 20, 2008

Downtown Winnipeg still frost free

Although freezing temperatures have been recorded across most of southern MB by now, the growing season continues in downtown Winnipeg which has still to register a below freezing temperature so far this fall. The lowest temperature so far at the Forks weather station downtown has been 0.3C on Oct 17th.  This morning, while the temperature at Winnipeg airport dropped to a chilly low of -4.8C, the Forks station recorded a low of +1.5C, over 6 degrees warmer than the airport site.  This difference is due to a phenomenon known as the "urban heat island" effect, which basically keeps temperatures (especially nighttime temperatures) warmer in a downtown core compared to nearby rural areas which can lose heat to the environment more effectively. This prolongs the average growing season downtown by 2-4 weeks compared to the airport site. 



  1. Forks station recorded its first freezing temperature of the season late Oct 26th.. finally ending the growing season downtown for 2008. This is a full month later than the Winnipeg airport site which posted a -0.5C reading on Sept 27th. The last freezing temperature in the spring at the Forks site was a -0.1C reading on May 11th.. resulting in a frost free season of 165 days downtown. Compare this to the Winnipeg airport site which had an official growing season of only 116 days this year (June 3rd - Sep 26th), a full 7 weeks shorter than downtown.

    Here in Charleswood, my 2008 frost free season was 151 days from May 12th to Oct 9th, 5 weeks longer than the airport site.

  2. Ligt in winipeg het ijs, dan zit in het krentenbrood het ijs.