Iowa has experienced a spate of at least 19 tornadoes in the past two weeks, according to the National Weather Service (NWS), amidst severe weather across the Midwest. A May 22 tornado killed one person in Adair County, while other storms have resulted in damage to property.

Tornadoes are rated on the Enhanced Fujita (EF) scale in North America, from the least severe, EF0, with winds of 65-85 miles per hour to the highest severity, EF5, with winds of more than 200 miles per hour.

The Adair tornado was rated an EF2, with a trail on the ground of 4.8 miles and a maximum width of 150 yards, according to the NWS.

Justin Covert, a graduate student in geological and atmospheric sciences at Iowa State, said late spring and early summer are when Iowa sees the most tornado development.

“[Tornadoes develop] due to the interaction of cool air masses that move down from Canada with warm, moist air that comes up from the Gulf of Mexico,” Covert said. “When these air masses collide, it creates an ideal environment for thunderstorms, severe weather and tornadoes.”

Covert said Iowa, and the Midwest in general, is ideal for tornado development because it is where those two air masses come together.

“When low pressure systems move east out of the Rockies and into this environment with competing air masses, it results in very strong instability within the atmosphere that helps feed severe weather and tornadoes,” Covert said.

Covert said that the number of tornadoes should decrease in the next month, as typically most tornadoes in Iowa occur in May and June.

The National Oceanic and Atmospheric Administration (NOAA), a federal agency, advises what to do in the event of a tornado. People should to head to the basement or lowest floor of a building, avoid windows, get as low to the ground as possible, protect their heads and stay off of elevators, according to NOAA.

The NWS Des Moines was asked a question in a tweet about a possible correlation between temperature and severe weather Monday.

“In short, it’s June, expect severe [weather],” the NWS tweeted in reply.