I now have seven and a half years of weather data for my neighbourhood from the UVic Weather Network. This is still not enough for clear long term trends, but it does give me some reasonable data for the growing season.
Frost is any temperature below 0, a hard frost is -2.0 or lower.
First Frost of the Fall First Hard Frost Coldest Frost
2012 November 9th has not happened yet -0.9 November 9th
2011 November 1st November 15th -4.4 November 20th
2010 November 12th November 21st -8.7 November 23rd
2009 October 12th December 7th -7.7 December 10th
2008 November 26th December 13th -9.2 December 16th
2007 November 2nd December 31st -2.8 December 31st
2006 October 30th October 30th -6.6 November 29th
2005 November 26th December 16th -2.4 December 17th
From this data I think I can comfortably count on October stilling being a growing month especially for the hardier plants.
Last Frost of the Spring Last Hard Frost
2012 April 7th March 7th
2011 April 8th February 26th
2010 March 18th March 8th
2009 March 29th March 21st
2008 April 9th January 28th
2007 April 2nd March 1st
2006 March 19th February 24th
The last frost in the spring is fairly consistently within a three week period from March 18th to April 9th with four times the last frost being in the first 9 days of April. I think that April 15th is a reasonable day to assume we are safe from frost in the garden.
Length of the frost free period
2012 216 days
2011 207 days
2010 239 days
2009 197 days
2008 231 days
2007 214 days
2006 225 days
avg 218 days
Over the last seven and half years, there have only been 15 days when the daytime temperature did not rise above 0 degrees. The temperatures have only dropped to -5 degrees or lower on 16 nights in that same time period.