TULSA, Okla. (AP) – 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 was the longest the U.S. had 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.