Fox News Weather Center

Tornado season gets late start, heats up with rise in temperatures, humidity

  • 498e04e6ea9a6e10320f6a7067002ec2.jpg

    CORRECTS MONTH TO MAY This frame grab provided by KWTV shows a tornado in Oklahoma City Monday, May 20, 2013. Television footage shows flattened buildings and fires after a mile-wide tornado moved through the Oklahoma City area. (AP Photo/Courtesy KWTV) (The Associated Press)

  • 9eaea01aeaca6e10320f6a7067006872.jpg

    A woman carries her child through a field near the collapsed Plaza Towers Elementary School in Moore, Okla., Monday, May 20, 2013. A tornado as much as a mile (1.6 kilometers) wide with winds up to 200 mph (320 kph) roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods, setting buildings on fire and landing a direct blow on an elementary school. (AP Photo Sue Ogrocki) (The Associated Press)

The tornadoes that have raked communities in Oklahoma, Texas and other states over the past week belie what has been an unusually slow start to the 2013 tornado season.

In fact, this is the longest the U.S. has gone into May without registering an EF1 or stronger tornado, which are the types that can cause damage. That's according to Harold Brooks, a research meteorologist at the National Severe Storms Laboratory.

A cool spring in the nation's midsection kept the funnel clouds at bay about a month after they'd typically begin their deadly dance.

The calm has melted away with a recent rise in temperatures and humidity that has allowed for the ideal conditions that have given rise to deadly twisters in Texas and Oklahoma since last Wednesday.