The US is experiencing the coldest spring on record, and the quietest year for tornadoes. Experts say this is due to an overheated atmosphere caused by your failure to purchase a Prius.
Updated 2 May 2013 to correct typo on date of previous low tornado count
The 12-month period from May 2012 to April 2013 was remarkable for the absence of tornado activity and tornado impacts in the United States.
We can start by looking at the number of EF1 and stronger tornadoes during that period. A final count is available through January 2013 and we have a pretty good estimate of how many occurred in February through April, although final numbers won’t be available until July. Although the 12 month total may change a little bit with the final data, it’s unlikely to change enough to affect the results here.
From May 2012-April 2013, the estimate is that there were 197 tornadoes rated EF1 or stronger. Where does that stack up historically? Well, we have pretty good data back to 1954. During that time, the previous low for (E)F1 and stronger tornadoes in a 12 consecutive calendar month period was 247, from June 1991-May 1992. The next lowest (ignoring the overlapping periods, such as April 2012-March 2013) was 270 from November 1986-October 1987. The lowest non-overlapping 12 month counts on record from 1954-present, with the starting month, are:
197 May 2012 (preliminary)
247 June 1991
270 November 1986
289 December 2001
298 June 2000