The recent La Niña in the Pacific Ocean is bringing tornadoes to Iowa.

There have been 35 tornadoes in Iowa as of April 20, about 25 more than the average number for this time of year, said Iowa State University meteorology professor William Gallus.

The typical peak tornado months of May and June have yet to arrive.

“Fifty-one would be the average for the year and normally by now, we would have only had nine or 10,” Gallus said.

Gallus said the La Niña occurring in the Pacific Ocean has led to strong storm systems across the country and may continue into the summer.

A La Niña event occurs when Pacific trade winds push warm water to the west, bringing cold water to the ocean’s surface. With this, the jet stream gets stronger and creates an environment for more storms to occur in certain parts of the U.S.

Gallus said during La Niña years, the jet stream typically points to the southeast, causing strong storms to occur in the region.

In April, however, the jet stream was aimed directly at Iowa, causing several strong storm systems that have also kept warm air out of the area, Gallus said.

“Everything’s been moving along so fast that when we’ve managed to get some warm air, it’s usually been when we’ve had those tornadoes and the warm air comes in for part of a day,” he said. “Then it’s quickly swept away, and the winds swing back around to the north.”

While tornadoes have been active, with over 95 occurring in Iowa since December 2021, Gallus said he expects early May to be a bit calmer because of lower temperatures than usual.

Despite this, he said, it’s likely Iowa will surpass its annual tornado average of 51 this year.

Gallus said more tornadoes will likely occur in Iowa in late May and throughout June, though how many more depends on the La Niña.

If the jet stream continues to point north, there will likely be more tornadoes in Iowa during that period. If it pivots to the South, there will still be tornadoes in the state, just not as many, he said.

The 35 tornadoes that have hit Iowa in 2022 have come shortly after the tornado outbreak from December 2021, when 63 tornadoes hit the state.

Rich Kinney, National Weather Service warning coordination meteorologist in the Quad Cities, said while a single tornado outbreak can’t necessarily be attributed to climate change, climate researchers are finding that the potential for severe weather is expanding over more of the year.

Gallus said it’s difficult to say how much climate change has contributed to the formation of tornadoes, though climate change can increase the chances of severe weather.

“Warmer air adds extra energy to the thunderstorms,” Gallus said. “That would help [to form] tornadoes, but because the warming is greatest near the North Pole and the South Pole, that actually tends to try to weaken the winds in the atmosphere. So that would make it harder to get a tornado.”

Chad Hahn, National Weather Service warning coordination meteorologist in Des Moines, said the high number of tornadoes observed in recent years can be partially attributed to enhanced detection technology.

Now, he said, meteorologists can use satellite images to identify tornadoes, even those that don’t cause any visible damage.

“Years ago, it would have to be, somebody reported damage that had to be visible from the ground survey,” he said. “And then we had to connect the dots that way.”