The old joke goes, whenever any nervous service provider asks you for a tip, is to give them a life tip, rather than a monetary one, such as, "Plant your corn early". Unfortunately for Albertans, "early" can be a difficult point to identify. One certainly wants to plant corn after the threat of frost has passed and get that corn crop off before the frost returns in the fall. Unfortunately, however, frost figures for Alberta municipalities vary widely. This variance is thanks to extreme differences in such factors as elevation, latitude, urbanality and the presence of groundcover.

"Frost-Free Period" has nothing to do with refrigerators

The Alberta government compiles statistics using historical data to arrive at an average First Frost-Free Day and First Frost Day for most municipalities in the province. The interval in-between is the Frost Free Period, or FFP, for every location. As one would expect from such a large and widely diverse region as Alberta, the length of the period can vary from reporting location to reporting location by as much as 100 days.
Before we announce the winners and losers in the FFP sweepstakes, it should be mentioned that, although geographic factors do play a large role in an individual municipality's score, some of the values seem inexplicable. Regions one would think should be similar often are not even close. These stats don't really indicate the "why", however, just the stark FFP score.

And the Winner is...

According to the data, the Village of Duchess, which is close to the city of Brooks in the sunny south of the province, has by far, the longest FFP among the reporting stations. Their average last day of frost for the year comes on May 8 and the fine citizens of the village (Duchessians? Duchessites? The Duchessese?)  remain frost-free until Sept 18. This is a whopping 131 days which significantly impacts on the region's growing season. Whereas the usual rule of thumb for most prairie based vegetation enthusiasts is not to plant the garden until after the Victoria Day May long weekend, The Duchess can probably safely start a full two weeks earlier.

Latest but not least...

One surprising finding, while sifting through the data, was the town which boasted the latest arrival of frost.  Although the folks from Breton are fairly central in the province and not in the warm south, they have to wait until Sept 29 to see their first film of pumpkin icing. That frost remains, however, until May 24 which is usually after "Maylong" and the tradition kick off to seedy adventures.
Consider, too, the Town of Winfield, which is just 18 km south from Breton.  Winfielders can usually count on seeing frost on the ground until June 1; a full week after their "next door neighbors". They also see frost significantly earlier than their Bretonite brethren with its annual arrival scheduled for Sept 1. This is a difference of an incredible 35 days in FFP terms despite being located just 11 miles away.

A real head scratcher

FFP anomalies are also apparent around the province's Capital Region. Edmonton's International Airport, situated south of the city, reports their FFP goes from May 24 to Sept 10 for a total of 107 days. Contrast that with the more northerly Edmonton/Namao Airport station which lists their FFP from May 12 to Sept 21, or 130 days; an extra three weeks more than the EIA. 

To check out your own municipality's Frost Free Period, click this handy link to the Alberta Agriculture and Forestry website.