The official start of winter is more than a month away, but New York City is experiencing an early preview.

A deep dip in the jet stream has ushered in cold arctic air and sent local temperatures plummeting. After reaching an unseasonably warm high of 65°F on Wednesday, the high in Central Park today was only 42°F. That is a difference of 23°F in just 48 hours. The city’s normal high for this time of year is 54°F.

The cold air also helped produce the city’s first snowflakes of the season. While nothing accumulated on the ground, the National Weather Service reported a trace of snow in Central Park early Friday morning. A trace of snow is defined as less than 0.1 inches.

Unlike earlier cold snaps this season, these current chilly conditions are expected to linger for at least a week.