Autumnlike Chill on the Way

Invasions of chilly air from the north become increasingly common during thesecond half of September and October. Up north the air is growing colder by theday, mainly because all effective sunlight has been lost. Up around the ArcticCircle the sun is barely above the horizon this time of year and outgoing heatenergy greatly exceeds what is being gained.A cold front Friday will lower temperatures significantly across the northernPlains and Montana. The chilly air will reach the Midwest and Great LakesFriday night and Saturday. Some of this cooler weather will be felt across theNortheast Sunday and Monday.