Wisconsin is almost at yearly average of tornadoes already in 2024

With 22 tornadoes already in 2024, Wisconsin is almost at its average tornado count for the year.

Typically, Wisconsin has 23 tornadoes in a year, according to National Weather Service data. But, with 15 tornadoes on May 21 alone and with June historically the month when most tornadoes occur in the state, Wisconsin is almost certain to beat the average — and maybe by a lot.

“May has just been a pretty active month overall across the state in terms of severe weather,” said Andrew Quigley, a meteorologist at the NWS Milwaukee-Sullivan office “Climatologically speaking, June is our most active month.”

On May 21, three rounds of storms swept across the state, with the latter two bringing severe weather and leaving tens of thousands without power.

Most of the tornadoes occurred in north central and western Wisconsin, Quigley said. That storm system was part of greater severe weather in the Midwest, including in Iowa, where a tornado caused heavy damages and four died.

Another system created two tornadoes May 7, with another three occurring Sunday, he said. Those were all in south central Wisconsin.

Two tornadoes occurred in February, a month when Wisconsin had never had a tornado, Quigley said.

How strong are tornadoes in Wisconsin historically?

Of the February tornadoes, one was the strongest of the year, at an EF-2 rating. It touched down near Evansville, in south central Wisconsin, on Feb. 8, and lasted for 26.2 miles, according to NWS data.

A tornado’s rating is based on what’s called the Enhanced Fujita Scale. A EF-2 rating, like the Feb. 8 tornado, brings winds between 111 to 135 mph. The highest rating is EF-5, with winds over 200 mph.

Wisconsin's last EF-5 tornado was on July 18, 1996, in Oakfield in southern Fond du Lac County. Injuring 19 people, the tornado destroyed 45 homes, five businesses and 130 other buildings, causing roughly $50 million in estimated damages.

Most tornadoes in the state are EF-0, EF-1 or EF-2. All but one of this year’s tornadoes have been below an EF-2.

According to data kept by NWS from 1950 through last year, Wisconsin tornadoes break down by rating as follows:

• EF-0: 498 tornadoes

• EF-1: 558 tornadoes

• EF-2: 266 tornadoes

• EF-3: 53 tornadoes

• EF-4: 18 tornadoes

• EF-5: 3 tornadoes

“The majority of storms don’t even produce tornadoes … it’s a small subset of storms already that can come together and produce tornadoes,” Quigley said. “But it’s even a smaller fraction of those storms that are capable of producing strong to violent tornadoes.”

Why are so many tornadoes occurring in Wisconsin?

It’s common for people to point to weather phenomenon like El Niño or La Niña, or climate change as reasons for the number of tornadoes in the state, but Quigley said it’s not an easy thing to explain.

He pointed to the jet stream — strong winds in the upper levels of the atmosphere — that has consistently been affecting the region. With that, Wisconsin has been in the warmer side of the jet stream and, subsequently, a train of weather disturbances in the state this month, leading to more thunderstorms.

Quigley contrasted Wisconsin’s weather with other states in the Midwest that have been in colder portions of the jet stream, bringing erratic weather there, including snow this month.

“It is very difficult to directly relate very localized phenomena … to something like a broad topic of climate change or a phase like El Niño or La Niña,” he said. “We just have been in a very favorable pattern, specifically in the month of May.”

This article originally appeared on Milwaukee Journal Sentinel: Wisconsin tornadoes are almost at yearly average already in 2024