Dear Tom,
Why does Lake Michigan lake breeze occur in Chicago when there are no storms in the area or even in the region?
—Neal Mendelson, Chicago
Dear Neal,
Actually, ideal lake breeze conditions occur in the absence of storm systems. The lake breeze is a phenomenon that occurs when air over the lake cools due to contact with chilly lake water and then blows inland. This happens regardless of other weather events that may be occurring. Air over the lake will be cooled from below whenever its temp is higher than the surface temp of the lake water. If larger scale environmental winds are not overpowering, the colder, denser air over the lake will move inland, and we note this as the familiar lake breeze. The lake breeze results from air density differences between heavier, chilled lake air and warmer, inland air. The greater this temp difference, the stronger the lake breeze tends to be.