CHICAGO (CBS) — There’s no official start to patio season in Chicago.

It just simply happens when spring happens.

Problem is those spring temps haven’t quite stuck until now.

CBS 2’s Jeremy Ross has more on the start of the season.

Outdoor happy hour making its triumphant return in Chicago.

Something that some businesses have been waiting for.

There are an estimated 1,200 places to dine and drink outside in Chicago.

And several made their long awaited 2018 debut.

Steven Knight, of Wildberry says outdoor dining is an immediate boost to the bottom line.

Adding, until now, there’s been a spring sales slump compared to seasons past.

“Right around 10 percent. Maybe a little less,” says Knight.

“We haven’t had a spring like this is probably a good six or seven years. It’s been really cold and rainy,” says Sam Toia, President and CEO of the Illinois Restaurant Association.

Toia says the weather has hurt business.

But Mother Nature has a way of rebounding.

“You get a few days like this in a row, you’ll see your sales go up, and you’ll see your profit loss statement look better and make up for the first two weeks in April,” says Toia.

Phillip Rizzo of Tiny Tap says like most business on the Riverwalk, his is seasonal.

Rizzo calls Thursday a bonus for the bottom line.

Because they’d normally be open May through October.

But Thursday’s sun is driving the demand for drinks.

“When the weather’s hot and people are out here, we want to entertain,” says Rizzo.

Years ago, some restaurants with patios would open in February.

A tremendous change from what’s happening at this time.