Ag Weather Forum

Prairies Canola and Freeze-Damage Potential

Joel Burgio
By  Joel Burgio , DTN Senior Ag Meteorologist
High pressure indicated for the Prairies at the end of August has a Pacific Ocean origin, which limits the threat of a killing freeze. (Tropical Tidbits graphic)

Crop development for canola across the Canadian Prairies remains behind normal. There is some concern over possible damage to crops in event of an early frost or freeze in the region.

Of the major crops, the highest concern for potential freeze damage is with the canola crop. The most serious impact to crop yield and production for canola would occur with a hard freeze, when temperatures drop to well under 28 Fahrenheit (minus 2 Celsius), in an area where the crop is not yet mature. A light freeze and possibly even a frost on immature canola would likely mean quality reductions for the crop. Quality issues are most likely to occur on immature crops when readings fall to 32 F (zero C) or lower for an extended period of time during the night.

The normal low temperatures for the Prairies as of this date would be about 46 F (8 C) in the Edmonton area of Alberta, and about 50 F (10 C) at Regina, Saskatchewan. So, an air mass with temperatures averaging 14 to 18 degrees below normal would be needed now, in late August, in order to reach the first level for potential cold weather impact. This seems like a lot, until you realize that Edmonton has already had a low of 39 F (4 C) and Regina has already seen a low of 36 F (2 C) this week. Also of note, the normal lows detailed here are for the airports in each city. Typically, surrounding farming areas outside of the cities can be, and usually are, colder.

The forecast through Aug. 23 through Aug. 25 weekend depicts a variable temperature pattern for the region. Values do not appear to vary significantly from normal. The chances that readings would fall to levels capable of causing significant damage to canola appears fairly limited during this time frame. The early part of next week will see a weak high moving in, with somewhat colder conditions developing. This is a little more threatening to crops in the region, but even still nothing to be overly concerned with.

In the longer range, from Aug. 28 through Aug. 30, the forecast presents a potentially colder air mass for the Prairies. A strong low and upper-air trough are indicated over eastern Canada and a moderate surface high, with a value of 1026 millibars, is featured over southwestern Canada. This high, should it verify, would most likely mean lower temperatures once again for the region. The normal lows at the end of August are 2-3 degrees F or 1-2 degrees C colder than they are at this time, meaning it is somewhat easier to get cold at that date.

However, the strongest northerly air flow is a little too far to the east to generate conditions to be cold enough in key canola areas to do significant damage. Also of note, a surface high pressure center over the Prairies has its origination in the Pacific Ocean rather than northwest Canada. This means that conditions should not be as cold as they could be in the surface high had been allowed to stay over land for a longer period of time.

The bottom line: Another cold period will form in the Prairies at the end of next week, capable of dropping temperatures into the 30s F (zero-4 C), but this does not appear to be a significantly damaging cold event. In other words, readings are not expected to fall significantly below freezing (32 F or 0 C) except possibly in local areas. This pattern will be closely tracked as it concerns the potential for significant cold to damage immature canola.

Joel Burgio can be reached at



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