This map is based on observations from 220 Environment Canada Climate Stations between 1880 and 1993. Minimum station data requirement was 5 years of frost date data.

Annual last spring frost date at any location in any given year may vary by as much as 15 days. Based on the historical record of last spring frost dates, this map should be interpreted as identifying a reasonable date when in any given year when the last spring frost can be expected.