Urban heat island behind soaring 90° tally at Midway
June’s been a warm month. The month is running 6° above normal and 6.9° warmer than a year ago. But, the distribution of the area’s most intense daytime heat hasn’t been uniform. The impact of Lake Michigan and variations in Chicago’s urban environment has helped produce a huge spread in the total number of 90° days at the city’s various weather observation sites. Midway Airport, with its heat retaining highly urban surroundings, leads the pack with 12 while O’Hare has just 7 on the books. But, Northerly Island’s tally of just four 90s underscores the impact of cooling lake breezes. Average June, 2005 temperatures are also illustrative. Midway’s 75.8° exceeds O’Hare’s 73.6° and Northerly Island’s 71.4°.
Wednesday’s SE winds do little to reduce humidity levels. The flow should limit lakeshore highs to 78-84°. Low 90s are likely several miles inland. A final day of 90s is due Thursday.
-Tom Skilling