At a time when restaurants typically put away their patio furniture, sweaters replace T-shirts and sailboats are plucked from the water, Midwesterners are out enjoying activities usually reserved for July and August — not weeks past Labor Day. Summer is here. Finally.

"We're getting the summer we never had and now we're making up for it," said Bill Snyder, who produces the weather segments of the WGN-TV news in Chicago.

Alyssa Theisen certainly did. The 4-year-old, wearing a dress, darted right into a fountain in Chicago's Millennium Park on Wednesday, surprising her mother.

"She just ran into the water," Angie Theisen said. "I didn't bring her (swim) suit. I thought it was too late."

At Chicago's Monroe Harbor (search) on Lake Michigan, sailors thought the water would be a lot less crowded.

"Very few boats are gone for the season," said Joe Williams, the harbor master. "The weather is keeping them in the water."

Blocks away at Rock Bottom Brewery and Restaurant, general manager Nicole Allison said the rooftop patio is more crowded than it's ever been in September.

"Typically this time a year we close (the patio) past sundown — it's too chilly," she said. "Now we stay open up there until midnight."

How weird is it? In Chicago, Wednesday marked the 14th day of the month with temperatures reaching 80 degrees, and Thursday was expected to be the 15th. In August there were 10.

"You might as well throw your calendar away," said Shawn Joyce, a Chicago police sergeant keeping an eye on a lakefront beach peppered with sunbathers.

It's looking like this will be only the fifth September in Chicago since records started being kept in the late 1800s that will end with an average high temperature above the average high for August, Snyder said.

It's the same story in other parts of the Midwest.

In Iowa, state climatologist Harry Hillaker said he expects September to end up being warmer than August for only the second time in the state since 1897.

In Minnesota's Twin Cities, September is well on its way to being the sixth warmest on record, following an August that was the sixth coldest, said Pete Boulay, assistant state climatologist. It was 84 degrees on Wednesday afternoon. On Aug. 10, the high was 59 degrees.

Snyder said it has been sunny 89 percent of the time that it could possibly be sunny this month in Chicago. Normally, it's far cloudier in September and the sun shines 62 percent of that possible time.

"If the month ended today, this would be the all-time sunniest September since 1885," he said.

Experts say the reason the Midwest cooled down when it is normally warmer and heated up when it would usually cool off was two unusual weather patterns, one after the other.

During the summer months, there was a dip in the jet stream over eastern Canada and the eastern United States, said Paul Merzlock, a National Weather Service (search) meteorologist. That was pulling polar air from northwestern and central Canada through the Midwest, causing temperatures to drop.

In Chicago, that translated to just three days with temperatures reaching the 90-degree mark, Snyder said. A typical summer will have 18-21 days that hit at least 90, he said.

This month, an unusually strong high pressure system parked to the east over the Ohio Valley.

"When one sits in one spot, that tends to slow down other systems," Snyder said. "Normally, cold fronts would move through here a lot faster."

More typical fall weather is poised to return to the Midwest as soon as Friday, according the National Weather Service.

Until then, Mike Rogers is savoring the sun.

On a normal weekday in late September, Rogers might grab a quick lunch and head back to work. On Wednesday, the only thing he worked on was his tan.

"This has been gorgeous," said the 43-year-old engineer, as he lay on the lawn of a downtown park in shorts, his shoes serving as a pillow. "You don't want this to end."