ST. LOUIS — After a chilly Thursday afternoon across the bi-state region, diminishing winds and a clearing sky will set the stage for the coldest night so far this autumn for most of us.
As the sun sets, temperatures will drop quickly. Winds will become light if not completely calm after midnight. The air that blankets the region is quite dry. The clear sky, light wind and dry air make the perfect recipe for exceptional radiational cooling. This will allow for temperatures to drop close to or below freezing by daybreak Friday for some of us.
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The National Weather Service has issued a freeze warning for areas south and east of St. Louis and a frost advisory for the rest of the area from 3 a.m. until 9 a.m. Friday. Frost is expected to form in most areas. Temperatures below freezing can be expected in the area covered by the freeze warning.
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Tropical plants and annuals that are not frost-tolerant should be protected. Cover plants with an old sheet or light fabric that is breathable. Newspaper and paper bags may be used as well. If a plastic covering is used, it should be removed as soon as temperatures warm a few degrees so as to not damage the plant.
With plenty of sunshine Friday, temperatures will quickly warm into the 40s and 50s. By the afternoon, we will climb into the lower 60s.
Saturday will be much warmer with high closer to 70 degree. Rain chances return Sunday.