It’s a matter of degrees and every one matters.

Temperatures around St. Paul hit -10 C on Sept. 11, and that’s very unusual, said provincial crop specialist Neil Whatley.

“That’s a pretty heavy frost, but there’s humidity in the air. The dew will protect a lot, especially those that are -2 or -3,” he said. “It depends how many hours it was cold.”

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Frost in the -1 to -2 C range is not severe, but anything lower can cause significant damage if the crop is not ripe, he said. Yield and quality will be lost when cereals are at the mid- and soft-dough stages, and show signs of shrivelled, shrunken kernels. At -4 C, frost can kill crops.

Canola does better because seeds in the lower parts of the canopy are more protected and producers can hold off harvesting until the bottom seeds mature. However, if severe frost freezes those lower seeds or if the branches between the main branch and the pods may break and “start falling to the ground, then you want to get out there and get swathing,” said Whatley.