Brutally cold temperatures, icy winds, and heavy snow accompany what we commonly call a polar vortex in the winter, but the polar vortex is a dynamic system of interacting forces that exists year-round. When the winds that rotate around the North Pole weaken, cold air escapes to the south and temperatures plummet. In 2019's polar vortex, wind chills in Chicago were 50 degrees below zero and the air temperature dropped to minus 23 degrees Fahrenheit. But wind chill, by itself, usually doesn't affect plants; it's the actual air temperature that can cause harm. Snow can be useful in the winter garden, providing moisture and protection.