More multi-tornado days in the forecast for U.S.
Since the 1970s, number of days with more than 30 twisters has increased
TWISTED The number of days per year with tornadoes has gone down over the last few decades in the U.S., but the number of days that see 30 or more twisters is going up.
Justin Hobson/Wikimedia Commons (CC BY-SA 3.0)