The coldest air of the season so far will flow into the Southeast this weekend as an Arctic front moves through the region on Friday night. It will bring sub-freezing air as far south as northern Florida on Sunday morning. A big winter storm is expected to develop along the East Coast and the Carolinas could see significant amounts of snow, but Georgia, Alabama and Florida are not expected to experience wintry precipitation, just the Arctic air. Crop farmers in southern Georgia may be glad to finally see freezing temperatures, which will kill off the regrowth of cotton plants and knock out overwintering pests and diseases, but it could cause big problems for blueberry producers since the air will be so cold and dry that frost protection may be ineffective. The trajectory map below shows that air from far northeastern Canada could end up as far south as Miami.
The weather that occurs over the weekend is expected to be a classic winter freeze event, with the first night experiencing the advection of the cold and dry air into the region with NW winds of about 14 mph and dewpoints that fall into the teens by Saturday morning. The second night the winds will die down, but with a dewpoint temperature in the single digits and clear skies all night, frost protection by irrigation is likely to be ineffective since most sprinklers cannot put out enough water to keep the temperature of the blueberry bushes near freezing, especially as temperatures will fall continuously as heat is radiated out to space overnight.
The hourly forecast for Saturday and Sunday for Alma, GA, is shown below; you can get your local forecast by following the instructions at Where to get hourly weather forecast information | Climate and Agriculture in the Southeast (uga.edu) According to this forecast, Alma is likely to see about five hours below freezing on Friday night into Saturday morning, although the minimum temperature is only expected to be 29 F. The windy conditions will make it difficult to produce good ice cover on blueberry bushes. On the second night, Saturday into Sunday morning, the wind will die down to about 2 mph and the temperature will fall below freezing for about 12 hours, with a minimum temperature of 23 F. Normally, frost protection by irrigation is ineffective at temperatures of below 23 F in calm winds, and irrigation in those circumstances could cause more damage to the bushes from the weight of the ice.
I wish I had better news for the blueberry farmers. Of course, this forecast is still a couple of days out, and there is some variability in the different model runs, so we could see somewhat different weather when the front comes through, but the likelihood of a significant freeze event is high all the way into northern Florida.
You can find some information about frost protection using irrigation at:
Frost forecast for Saturday morning:
Frost forecast for Sunday morning: