Dear Tom,
We recently moved to this area and wonder why the lakefront is cooler during the spring and summer, but warmer during the fall and winter?
— Gerry and Mary Deppe, Evanston
Dear Gerry and Mary,
Lake Michigan is Chicago’s natural air conditioner in spring and summer, but often warms areas near the lake in fall and winter. Water has a high specific heat, making it slow to warm in spring and slow to cool in fall. On warm days when winds are light, the heated air over the land rises, allowing the cooler and denser air over the lake to flow onshore, delivering a cooling lake breeze. During the cold season, when the lake is warmer than the air, onshore winds bring the warmth inland. In late fall or early winter this lake-enhanced warming can cause it to rain in areas near the lake while snow is falling farther inland.
