April 21, 2007

The weather in Chicago really does seem fascinating, especially at this time of year. Every town seems to feel it has the most fickle weather--living in Richmond, Va., the meteorologists claimed the combo of the mountains and ocean made the weather there unique. Of course, weather everywhere is unique. Everywhere, it seems, people use the phrase "if you don't like the weather in [insert city name], just wait five minutes and it'll change."

On Tuesday, while positioned at my cubicle, I checked the current weather on the Chicago Tribune Web site. The temperature in north suburban Libertyville was 43 degrees. At Midway, a few miles from my cubicle, the temperature was 70. I later learned this wasn't a misprint. There was a 40-degree temperature gradient in the Chicago area. In the South Suburbs, temperatures topped 80 degrees for a time. This was due to a backdoor cold front.

These sort of temperature differentials are common here in spring. Many days, O'Hare Airport and points inland will reach 70 degrees but it will be 50 here along the shores of Lake Michigan. According to meteorologist Tom Skilling, chilly winds blow off the lake 42 percent of the time in April. The lake remains cold well into spring. Right now, water temperature is 37 degrees (coldest on this date in four years according to Skilling). The lake's thermal inertia keeps shoreline areas chilly much of the time well into May and even June. On some spring days, we are one of the coldest places in the Lower 48. Tomorrow, I hope to bird at Montrose Point, which is surrounded on three sides by Lake Michigan. Only on the warmest spring days do Southwest winds overcome the cold there, and tomorrow warmth is forecast.

The lake, though, makes up for it in fall. The same inertia ensures the growing season along the lake lasts into November. There's an incredible graphic the Tribune occasionally publishes that shows the contours of the growing season from the lake inland. There's a variance of nearly a week for every mile moving west from the lake.