Arctic cold is a common occurrence across the Canadian Prairies during the winter as it slides southward from the Yukon and the Northwest Territories from time to time. The degree and persistence of this extreme cold can vary considerably from year to year depending on the overall weather pattern that sets up.
Winter wheat has shown some increase in acreage across the Prairies during the recent few decades and its survival during the winter depends quite a bit on how much snow cover exists during periods of cold weather. Snow cover acts as a warming blanket and is an excellent insulator.
Research done by North Dakota State University and the U.S. Department of Agriculture show that only a few inches of snow can greatly benefit winter wheat during times of cold. It is generally accepted that 3 inches (8 cm) of snow can prevent winterkill, but that 4 to 6 inches (10 to 15 cm) of snow depth will further reduce winter injury.
Soil temperatures at crown depth have been shown to be as much as 30 to 35 degrees F higher with 2 to 4 inches (5 to 8 cm) of snow cover while readings of 40 to 55 degrees F higher can occur with 5 inches (13 cm) or more of snow. The study was based on air temperatures of minus 22 to minus 40 F (minus 30 to minus 40 C), which are temperatures seen several times during a typical winter across the Canadian Prairies.
When crown depth temperatures fall to minus 5 F (minus 21 C) or lower, we see a rapid increase in winterkill, but with a few inches of snow crown depth temperatures may only be a few degrees below freezing, allowing for a good survival rate.
Current snow depths across the central and southern Prairies are in the range of 2 to 8 inches (5 to 20 cm) with lesser amounts across southern Saskatchewan. Temperatures have been lower than normal during the past few weeks across the Prairies, but no extreme readings have yet to appear and most areas currently have enough snow to protect winter wheat.
A couple of low pressure areas moving through the region during the next week may add to the current snow cover and we are not expecting any extreme cold in the short term. Beyond 10 days, there are signs that some arctic air may arrive and send temperatures to well below zero F (minus 18 C). Hopefully we will continue to have the protective snow cover for winter wheat still in place.
Doug Webster can be reached at firstname.lastname@example.org