Dear Tom,
Since the beginning of time has the dew point ever reached 100 degrees?


Harry B. Romeoville

Dear Harry,

It likely has, though record-keeping from the Jurassic Era left much to be desired. The world’s record for dew point temperature is a sweltering 95 degrees logged on July 8, 2003, at Dhahran, Saudi Arabia, on the Persian Gulf. With a 95-degree dew point, the lowest possible heat index (temperature 95)) would be 161. Surprisingly, some of the highest verified U.S. dew points were not observed on the Gulf or southeast Atlantic coasts but in the Midwest, fueled by evapotranspiration from the maturing corn crop. Weather historian Christopher C. Burt reported that it reached 88 at Moorhead, Minnesota, on July 19, 2011, 88 at Newton, Iowa, on July 14, 2010, and 90 at Appleton, Wisconsin, on July 13, 1995. Chicago’s highest dew point: 83 on July 30, 1999.