Explaining the Tigers-White Sox bizarre rain delay Monday night

(FOX 2) - Deep in the Tigers-White Sox game, sheets of rain began pouring over the stadium, sending fans fleeing and grounds crew out to cover the baseball diamond.

Minutes before the downpour, the radar didn't show any rain in the forecast. It delayed the ending of the game by an hour during the bizarre occurrence. 

Big picture view:

In the top of the 9th inning, with two outs and two batters on base, the Detroit-Chicago baseball game was treated to some summer rain that came out of nowhere.

Thousands of fans hoping to see the game through to the end instead ran for cover as a downpour ensued. After an errant pitch, it became clear it was much too wet to continue play, leading to an hour-long delay. 

The Tigers-White Sox rain delay

While rain delays are not unusual for baseball, this latest case was a strange one. The Tigers play-by-play commentator said the rain came "out of nowhere."

It's true the radar from the National Weather Service showed nothing in the forecast before the rain arrived. But when it did, most of Chicago was covered with showers that spawned almost immediately.

And not just the mild showers indicated by green on the radar - but yellow, orange, and red too, which pack quite a punch for anyone caught under the precipitation.

So what happened?

FOX 2's Derek Kevra took a look and found that the ingredients for a strong storm were already in the air. Like in Metro Detroit, Chicago is dealing with its own high dew points with plenty of moisture in the atmosphere. 

"But it needed a spark," he said.

To go from wet muggy humidity to rain, there needs to be a catalyst. In the case of Monday's Tigers-White Sox game, a likely breeze from Lake Michigan blew over northern Illinois, creating a deluge at Rate Field.

Dig deeper:

Pop-up thunderstorms are more common in the south, but they do happen in the Midwest. As the sun heats the Earth, land warms up faster than water. As the sun sets and temperatures dip, a pressure difference is created.

The air over the water then moves in, and rises, bringing all the moisture in the air with it. Once it gets high enough, water condenses into rain before falling back down to Earth.

Lake Huron and Lake St. Clair have a similar impact in the air over Metro Detroit, which helps explain some of the pop-up showers that Southeast Michigan has received over the past few weeks.