Dear Tom,

Is there a temperature below when it is not possible for snow to form? What is the lowest temperature on record for measurable snowfall in Chicago?

Thanks, Fred Kviz, Oswego

Dear Fred,

It’s a question that we’ve been asked many times; it can never be too cold to snow. The lower the temperature, the less water vapor in the air, so any snow that falls at very low temperatures certainly would not be heavy, but it has snowed in Antarctica with temperatures lower than minus 70. Chicago weather historian Frank Wachowski remembers one super-cold Chicago snow event. On Jan. 10, 1982, nearly an inch of very-fine crystalline snow fell at Midway Airport when the temperature was as low as minus-17. Wachowski also noted that measurable snow has occurred on 14 other days with that recorded a reading of minus 15 or lower, though readings were warmer than minus 15 when the snow actually fell.