The cold air mass is expected to impact millions across the Great Lakes and Northeast, particularly in higher terrains where frost or freeze conditions are likely. Urban areas and regions near the Great Lakes may avoid frost due to residual warmth from water temperatures and the urban heat island effect. The sudden temperature drop may catch residents off guard, especially after last week's highs in the mid to upper 80s °F (29-31 °C). Frost-sensitive vegetation and outdoor activities could be affected, and residents should prepare for colder mornings. (Source: Weather Forecast Now)