My wife and I just returned from our winter home in Gilbert, Arizona. One day the humidity was 1 percent. What’s Chicago’s lowest humidity? And the world’s?
--Bob Hansen, Lindenhurst
Chicago climatologist Frank Wachowski reports that the city’s all-time low relative humidity is 13 percent, recorded on three occasions. It first occurred during a dust storm on May 10, 1934, and was tied on April 11, 1956, and April 8, 1971. Chicago’s low humidity episodes generally occur on warm, windy afternoons when dry air aloft can easily mix down to the surface. For the record, one of the world’s lowest humidities was recorded Oct. 24, 2006, in Coober Pedy, Australia, when a temperature of 93 and a dew point of minus 23 produced a relative humidity of less than 1 percent.