The map above shows the average date of the final -3 C frost in Alberta. Click here for more Alberta frost maps. Look under the “Atlas” tab and click on “Agroclimatic atlas” to find the frost maps.
The map above shows the average date of the final frost (based on data up to 2010) in Saskatchewan. Here is a larger PDF: Last_Frost_Spring
The Manitoba map showing the average date of the last spring frost is from here.