Forecasters warned of possible freezing weather in some southern areas as well, CNN reported.
In the Midwest, subzero wind chills were reported at Chicago-area airports at about 8 a.m. Wednesday, the Chicago Tribune said. The area was getting a blast of arctic air with highs forecast in the mid 20s.
This vernal equinox is the second in a row with abnormal weather in the Windy City. Last year, the high was a sultry 85 degrees while normal for the day is around 50.
In Maine, a late-winter storm dumped inches of snow, CNN said.
The National Weather Service warned of freezing temperatures in an area from Alabama to North Carolina, advising farmers to do what they can to protect crops.
The equinox is an astronomical phenomenon, the day the sun crosses the equator bringing days and nights of equal length around the world. The weather depends on factors including latitude and elevation as well as the length of the day.