Yeah, we know it's been cold and rainy in Wisconsin. Blame the jet stream.

Before Wisconsinites start griping about this spring's unusually cold, wet weather – What? Too late? – know this: 

The reason why Wisconsin hasn't been hit with tornadoes, thunderstorms and floods plaguing other parts of middle America  is because of our cold, wet spring.

Sure, folks have had to wear winter coats to Little League games and polka dancers at Polish Fest bundled up last weekend. Youth soccer leagues have been rained out and farmers' crops are way behind.

It seems like spring never arrived and summer has so far been mostly a no-show. Aside from slugs, few Wisconsin inhabitants are happy about this.

It has been relatively cold and crummy this spring because of the jet stream flowing consistently out of the Canadian provinces of Alberta and Saskatchewan, which has created a trough of cold air over the Great Lakes, said Andy Boxell, a National Weather Service meteorologist based in Sullivan.

That has kept humid, warm air well south of Wisconsin.

"We've really just been on the persistently cool side of all the systems coming through," Boxell said. "All the storms coming through the Plains have gone to our south."

A brutally cold winter and spring in the Dakotas, Montana and the Plains helped intensify and strengthen the jet stream, which was also boosted by a lot of activity pushing into the western and northwestern U.S. from the Pacific Ocean, said Dave Samuhel, a senior meteorologist for accuweather.com. 

Air stays stable

The recipe for thunderstorms calls for three ingredients – moisture, instability and a lift in the air from lower levels of the atmosphere. While there has been plenty of moisture in Wisconsin, there hasn't been much unstable air.

"We just have not been able to get the energy, the instability we need to get those thunderstorms up here," said Boxell. "I can count on one hand the number of days we've had dew points in the 60s, much less the 70s."

Dew point is the atmospheric temperature below which water droplets begin to condense and form dew. Dew points in the 50s are comfortable; when they get to the mid 60s, it starts to feel muggy.

The average temperature in Milwaukee for March, April and May – considered meteorological spring – was 44.5 degrees, around 1 degree colder than normal. However, May was almost 2 degrees colder than usual in Milwaukee; Madison also shivered through a May 2.5 degrees cooler than normal.

Eighty-degree days, and we've had a few, have been rare this spring and were usually followed by a 50-degree day.

Umbrellas and galoshes got a workout this spring, too. Almost half of March, April and May had some sort of observed precipitation, ranging from snow and freezing rain to rain and drizzle.

Milwaukee recorded 43 days of observed precipitation; the city averages 35 days of rain and snow during those three months. Mostly it's been light and drizzly with few soakers. Only nine of those days recorded more than half an inch of precipitation.

Winged blood-suckers in a holding pattern

A total of 11.7 inches of liquid-equivalent precipitation – rain and melted snow – fell in March, April and May. That is 2.5 inches above normal. Of those months, May punched well above its weight: 6.3 inches of precipitation, almost 3 inches more than the average.

While most of Wisconsin's 60 species of mosquitoes thrive on lots of standing water to lay eggs, the low temperatures have acted like a deep freeze because the nasty buzzing insects get lethargic when it's 60 degrees or colder, said P.J. Liesch, University of Wisconsin Extension entomologist.

Activity for many of the bug species calling Wisconsin home is about a week and a half behind average, a result of a late frost in some sections of the state and the colder than normal temperatures.

"It has been quieter than usual this year," said Liesch, who didn't have to pack bug spray when he went for a walk in Madison a few days ago, something he would normally do.

On the downside, that means pollinators such as bees and butterflies are scarce. On the bright side, gypsy moths, which can cause widespread defoliation of trees, and box elder bugs, which like to crawl into homes in the fall to find a winter shelter, are in bad shape.

Rainy weather can sicken gypsy moths and box elder bugs, making them more vulnerable to disease.

Slugs are not insects but Liesch gets plenty of calls about them from the public sick of seeing them in their gardens.

"It has been a decent slug year. With the rainy, overcast, cloudy conditions, they can really thrive," said Liesch.

Deja vu all over again

Spring 2018 was also miserable. 

"Last year we had our biggest snow of the season in April. This is our second year of what seems like a lengthened winter," said Boxell. "That adds to the perception that cold and rain are lingering longer than usual."

More unseasonably cool weather is in the forecast this week in southern Wisconsin, with slight chances for rain and possibly thunderstorms Wednesday and Thursday.

But the good news is the long-term forecast calls for a more average July and August,  with normal to slightly above-normal temperatures and near normal rainfall, said Samuhel. 

"The jet stream should lift far north into Canada and finally get out of our hair," Samuhel said. "You could get some thunderstorms but overall it looks like it will be a pretty typical summer."