Tornadoes can occur anytime of the year, so it is too early to answer this question.
(Photo credit: State Journal archives)
Tornado season is based on when the ingredients for severe weather come together in a particular region. Because a change in wind with height is closely related to the presence of a jet stream, tornado season moves north and south during the year with a jet stream.
Tornado season peaks in March and April in the Southeast but not until July in the upper Midwest and Northeast. The deep South has a secondary peak in tornado occurrence in November.
Tornadoes happen at any time of day or night. However, they thrive on solar heating and in some cases the ability of warm, moist air at the surface to penetrate a low-level capping inversion. Therefore, the most likely times for tornadoes are late afternoon or early evening. More than half of all U.S. tornadoes occur during the hours of 3 p.m. to 7 p.m. local time.
As of Friday, there have been 573 confirmed tornadoes in the U.S., causing 15 fatalities. The number of tornadoes puts this year at the 75th percentile climatologically.
The ongoing La Niña is predicted to continue through spring and possibly summer. La Niña conditions favor a more active severe thunderstorm and tornado season in the US.
Tornadoes are classified based on the damage the tornado does, which enables us to estimate the wind speed of its rotating winds. All tornadoes are assigned a single number from the Enhanced Fujita scale, abbreviated EF, according to the most intense damage caused by the storm. The weakest tornado is EF0, with winds less than 85 mph. The strongest is EF5, where the winds are greater than 200 mph. As of Friday, there have been no EF5 tornados, 15 EF3 and 2 EF4 tornados.
Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.
