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Dear Tom,
What are the best conditions for lake breezes to develop in Chicago?
—Jeff Rosen
Dear Jeff,
A lake breeze is a wind that blows from Lake Michigan onto the shore. It usually begins mid or late morning when tempera- tures over land become 15 to 20 degrees warmer than the lake water temperature (away from the shore — shore lake water temps are often higher than water temperatures farther out, in the open lake). Large scale winds over 10 mph usually are sufficient to defeat lake breezes.
Ideal lake breeze conditions develop when the area is dominated by high pressure. Wind- generating air pressure variations are small or non-existent. Lake breezes take over by day and land breezes blow from the opposite direction at night, with an intervening lull.