It’s That Time of Year – Talking Fall Frosts in Manitoba


As we enter in the later parts of the growing season, fall frost enters the minds of most people involved in the grain industry.  As everyone knows, frost can have an impact on a crop’s quality and yield.  There were a few areas reporting a light frost event the morning of September 14th.

The extent of frost damage to a crop will depend on several factors. The species, stage, and hardening of the crop, the soil type and soil moisture, the actual air temperature, the duration of freezing, and the rapidity with which freezing takes place are all important. A drop in air temperature of short duration will cause less damage than a prolonged periodthe same low temperature. When the air temperature drops to 0°C, cereal and other crops may not sustain damage. Rather, damage or total loss is more common when minimum temperatures drop below -2°C, often referred to as a killing frost.

Given its sporadic nature, long-range forecasting of frost is nearly impossible. Rather, the climate record of an area is used to determine probable dates of frost based on long-term temperature records. While this will not provide an actual frost date in a particular year, it will present the likelihood that frost may occur on a certain date. This can be a valuable planning tool.

The Manitoba Ag-Weather Program released updated FIRST FALL FROST MAPS in 2014 which are made from the new township gridded normal from a wider dataset of 1950-2010:

For additional information, please visit Manitoba Agriculture’s AgWeather Program at

Submitted by:  Pam de  Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture

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