Dear Tom,

I see that tornadoes occurred in eastern Iowa on January 16. How is that possible at such low temperatures?
David Alan Jone Ridge, Omaha, Nebraska

Dear David,

Most tornadoes occur with temperatures and dew points at least in the 50s, and that is what happened on January 16, as temperatures and dew points climbed into the lower and middle 50s across eastern Iowa ahead of the thunderstorm cluster that spawned the out-of-season tornadoes. Whatever was lacking in warmth and moisture was made up for by the storm cluster’s energy and strong rotation. However, there are always exceptions. Dr. Harold Brooks of the National Severe Storms Laboratory tells of a twister that struck at Altus, Oklahoma, on Feb. 22, 1975, with the temperature near freezing. The F-2 storm killed two and injured 12. Tornadoes have also been reported in areas with snow cover nearby. On April 10, 2011, an EF-3 twister hit near Merrill, Wisconsin., while area lakes were still frozen, and on Jan. 7, 2008, two twisters struck in southeast Wisconsin along the south edge of the snowpack. Low-temperature tornadoes are rare in Chicago, but on June 9, 1966, an F-2 twister struck Arlington Heights at 6 am with temperatures only in the middle 50s.