UPDATED 01/12/12 9 p.m.

CHICAGO (CBS) — Spring in January is officially over, as the first major snowstorm of the season blanketed the Chicago area, forcing airlines to cancel hundreds of flights and threatening to make a mess of the evening rush.

CBS 2 Meteorologist Megan Glaros reports a winter storm warning is now in effect for the entire Chicago area, from the Wisconsin state line south through Will County, through 9 a.m. Friday.

An earlier winter weather advisory was upgraded to a storm warning due to lake enhancement that will increase the intensity of the snow.

Snow was falling everywhere by 11 a.m. Thursday, as winds picked up. The worst time for the snow will be during the afternoon commute, Glaros says. The National Weather Service expects afternoon snow to fall at about an inch per hour.

The warning also affects Northwest Indiana and the west coast of Michigan, where up to 15 inches could fall.

MORE INFORMATION: EYE ON STORM | RADAR | CURRENT CONDITIONS | TRAFFIC | CLOSINGS | SEND PICS

As the temperatures drop over the course of the day, the snow will grow fluffier and harder to navigate.

Winds of 15 to 25 mph with gusts of 35 mph will cause blowing and drifting, and could cause a drop in visibility.

Altogether, most of the Chicago area will see totals of 4 to 8 inches. But from eastern Porter County, Ind., up along the west coast of Michigan, totals could top out at 8 to 15 inches.

The snow has already resulted in some headaches at Midway and O’Hare international airports.

At Midway, Southwest Airlines took the drastic step of preemptively canceling all flights into and out of the airport between 1 p.m. and 6 p.m. About 100 flights, or a quarter of all the flights at Midway, were affected.

LISTEN: WBBM Newsradio’s Regine Schlesinger reports

LISTEN: WBBM Newsradio’s Bernie Tafoya Reports

In all, more than 140 flights at Midway had been canceled by Thursday evening.

At O’Hare, more than 420 flights had been canceled, with delays continuing into the evening.

If you’re ticketed to travel Thursday or Friday on most of the major airlines, it’s likely you can get a waiver to change your flight. Travel waivers allow customers to make changes in advance of a storm or other major event, without the fees that would otherwise apply.

Travelers are advised to check their airlines’ Web sites for updates.

VIEWER PHOTOS OF THE SNOW

On the roads, the Chicago Department of Streets and sanitation initially deployed 184 snow plows on city streets Thursday morning, but by mid-afternoon had deployed its entire fleet of 278 snow fighting trucks to clean the city’s main streets for the afternoon rush.

“While all of the snowplows are working to clear the main arterial streets, falling snow and dropping temperatures can reduce visibility and make portions of the roadway slick at points,” said Department of Streets & Sanitation Commissioner Tom Byrne. “Motorists should drive with added caution during their evening commutes.”

The crews might not get to the side streets until sometime Friday, according to Byrne.

For the first time, the city is using its online “Plow Tracker,” through which residents can watch the snow plows in real time.

On the CBS 2 News at 11AM, Byrne said the plow crews have had to focus in particular on bridge decks.

“Actually, we’re concentrating real hard right now on the bridge decks that all became below zero, so we’re concentrating on the bridge decks and the surfaces that are starting to get a little icy,” he said.

While the overnight winter parking ban remains in effect, Byrne says he does not expect the 2-inch winter parking ban to be enacted this time around.

Further, Illinois Department of Transportation crews were busy overnight loading up their trucks with salt and mounting them with plows. They were out in full force Thursday on all area expressways.

IDOT advises motorists to give plows plenty of space.

“If folks are on the road, and they do encounter our plows and trucks, we’re advising them to give plenty of room for our drivers to operate,” spokesman Guy Tridgell said. “They’re heavy pieces of equipment that could take a long time to stop.”

Officials also advise building some extra time for the evening commute. IDOT even recommends taking public transportation if possible.

Even though the winter’s first significant snowfall didn’t come until mid-January, drivers and shovelers weren’t in the welcoming mood.

“We don’t need no more,” one man said as he shoveled his driveway in the Austin neighborhood.

Robert Burke, a veteran mailman, said snow slows him down and puts him at risk.

“You slip a lot of times, especially on the painted steps,” Burke told CBS 2′s Mike Puccinelli.

About 20 minutes after he said that, Burke’s fear was realized when he fell on the steps of a West Side house.

“My wrist is a little bit painful,” he said. “I slid all the way down the steps and my side hurts a little bit, but I guess I’ll be okay.”

Motorists say they expected snow Thursday, so they planned ahead.

“I think it’s pretty so far,” said Denise Hoit of Joliet, “and I plan on being done with work early enough not to deal with it. I started at 6 o’clock this morning, so I will be done by 1 or 2.”

“I kind of missed it, actually. I’m excited about it, a little bit,” added Jay August of Indiana. “Hopefully not too much of it, but a little is OK.”

But another man said of the snow, “I don’t want it. I don’t want it.”

Earlier in the morning, another woman was less than thrilled too.

“I hate snow. It’s never going to snow again in my lifetime. I absolutely hate it,” said Brenda Wiley, who was commuting from Chicago to Elgin Thursday morning. “I was praying they were wrong. That’s why I just played the lottery so I could win and stay at home.”

But with the snow inevitably coming, Wiley said she was taking safety precautions for the afternoon rush, “because I’m going to be in the midst of it. I’ll keep my fingers crossed.”