Ag Weather Forum

Harvest Weather and Frost Risk for the Canadian Prairies

Joel Burgio
By  Joel Burgio , DTN Senior Ag Meteorologist
The mean forecast maps covering the period Aug. 31 through Sept. 2, with the European model is on the left hand side, the U.S. model on the right, show the frost risk for the key growing areas of the Canadian Prairies remains below normal during the next week to 10 days. (Graphic courtesy of Penn State Meteorology)

As we near the end of August and look ahead to early September, the questions normally would revolve around the risk of frost in key growing areas of the Canadian Prairies and also the chances that rain would affect harvest progress or quality of crops currently being harvested.

This season, the region has experiences a good deal of hot, dry weather during the heart of the growing season which has likely pushed development of crops along at a normal or ahead-of-normal pace. This dryness and drought reportedly have greatly affected the spring wheat crop, but it appears to have had much less impact on canola and some other crops. The harvest weather going forward is probably more important than the risk of a frost or freeze, but I will give my ideas on both.

Harvest weather for the region continues favorable for at least the next seven days. Disturbances are moving in off the Pacific track by north of the mean ridge position in the west before dipping southward over the eastern areas.

This allows for some rain in northern areas of Alberta as the system moves through and overruns north of the warm front. As the systems dip down over the central and east areas, they run out of a moisture source until they are well past Manitoba and even well into Ontario.

Any rain chances during this timeframe are of a limited nature, sort of like the way the summer has gone to this point, and should not cause any undue concern for the harvest progress.

In addition, the temperatures trend towards above normal levels, which will also favor harvest progress and crop progress during this timeframe. Looking further into the future, the models do pick up on a system that appears to deepen more rapidly as it moves through the Prairies. This opens the door to some heavier rain potential in and near Manitoba, but probably not much elsewhere in the region. This system is a little too far out into the forecast period, coming late next week or next weekend, to be highly confident about. I would tend to lean more in the direction of less rain chance rather that more rain chances at this time.

The frost risk for the key growing areas of the Canadian Prairies remains below normal during the next week to 10 days. We are in a timeframe now, for the area, when even a moderately cold air mass could bring readings down to a level when frost or a light freeze becomes possible. A strong cold air mass at the end of August and the first week of September would likely mean a hard freeze for the area.

However, the only air masses I see now are either too weak or include too much Pacific air to allow for a strong or even a moderate cold threat to the region during the next week to 10 days.

Looking at the extended range maps covering the period Aug. 31 to Sept. 2, I see too much west-to-east flow and not enough north-to-south flow to allow for a significant cold weather outbreak.

This is a relatively new development. Looking at these same maps earlier this week, the models were forecasting much more north-to-south flow and a turn to colder conditions over northern Canada. This likely means that the models are having a difficult time resolving this weather pattern in the two-week timeframe.

Based on what I see today, I would expect that only minor cold air masses would move into the region late next week and early in the following week. This means some may see frost conditions with lows in the 30s Fahrenheit (2 to 4 Celsius) but the risk of colder weather would be less.

However, I will continue to monitor the situation for signs that may point more towards another cold weather risk, but the longer we go into the forecast, the less important this risk would become. It may also be the case, for many areas, that only a hard freeze would affect potential yields or quality and a frost or light freeze would do little.

As we look at the weather picture covering the next two weeks, it appears the chance for a significant rain event to affect harvest progress or quality is less than normal. It also appears that the chance for a significant freeze event occurring soon enough to make much difference is also below average for the date. However, the situation will continue to be monitored.

Joel Burgio can be reached at



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