Frost

Frost is an important event primarily because of its impact on agriculture. Both the length of the frost-free growing season and the occurrence of an abnormal frost within the growing season are important to crop yield and quality. Under climate change the frost-free period is expected to lengthen but mid-season frost events will continue to happen.

The impact of frost is often localized, with low lying areas hit hardest. The damage from frost varies by duration, temperature and affected crop. A frost lasting several hours at -2°C or colder is considered a killing frost. Unseasonable snow and frost hit the prairies in the summer of 1992 causing massive crop damage.

Figure 1: Date of Last Spring Frost
(Source: Saskatchewan Crop Insurance)

Figure 1 illustrates the date when the last spring frost can be expected (it may vary by as much as 15 days). The earliest date is May 1 to May 7 in west-central portion of the province and the latest is June 19 to June 26 – in the Cypress Hills and Duck Mountain uplands. In 2009 Saskatchewan experienced one of its coolest springs in 35 years. The risk of frost continued into July and crop development was delayed by 3 or 4 weeks.

Early fall frost can have the biggest impact on crop quality and yield. Figure 2, illustrates the average date of the first fall frost. For most of southern Saskatchewan it is September 9 to September 15.

On August 30, 2004 southern portions of Saskatchewan and Manitoba had a widespread killing frost, the earliest in 50 years. Low temperature records spanning 100 years were broken in Saskatoon and Yorkton. Broadview was the coldest spot at -2.9°C.

Figure 2: Date of First Fall Frost
(Source: Saskatchewan Crop Insurance)

Adaptation Actions

Adaptation for frost is primarily an agricultural concern.

• seed to maximize the growing season and avoid fall frost
• buy crop insurance
• seed crops that require a shorter growing season, or seed crops that are more resistant to early frost