BLOOMINGTON - State police are handling numerous traffic collisions and the Bloomington airport canceled all but early morning flights because of thick fog throughout Central Illinois. | Photo Gallery 1 | Photo Gallery 2

A few thunderstorms are possible this evening with possible small hail. There's a chance of thunderstorms Tuesday with heavy rain changing to freezing rain and then to snow Tuesday night, said the National Weather Service forecast. The high is predicted at 44 degrees and the low at 29 degrees Tuesday.

Illinois State Police Capt. Suzanne Jansky, commander of the police district based in Pontiac, said her troopers were at five separate crash sites, some with multiple collisions, about 3:20 p.m. She said many of the collisions were occurring along state and U.S. routes, such as Illinois route 47 in Livingston County and U.S. Routes 150 and 136 in McLean County.

"You've got traffic coming from a lot of different angles" as well as traffic control devices on the state and U.S. routes, as opposed to interstates that have controlled access and a median as a barrier, Jansky said.

And Pontiac-based officers were sent to the El Paso area, where there were some collisions involving semi trucks, Jansky said.

Unfortunately, people often don't see the risk of fog as readily as they do with other inclement weather, Jansky said. People need to drive slowly, use their headlights and seatbelts and adjust as possible to what other drivers may do.

"First and foremost, deliberate whether you need to travel," Jansky said. "If you do opt to travel, most sincerely, you are taking a risk by doing that."

And Jansky said drivers in the dense fog won't have the luxury of seeing and reacting in advance if other drivers make mistakes.

About 16 departures and arrivals at Central Illinois Regional Airport were canceled by 3 p.m., said Fran Strebing, deputy director of marketing for the Bloomington airport.

"I know the forecast is calling for a dense fog advisory through this evening," Strebing said, "And the airlines need one-half to three-quarters of a mile of visibility in order to operate."

Strebing later said, "We can't even see out our window at this point,"

The fog is a frustrating weather issue for airport officials, as other weather problems can be plowed or de-iced, she said.

Around the state, thick fog poured over much of Illinois on Monday, prompting officials to close Chicago's Midway Airport for much of the day and cancel hundreds of flights at O'Hare International while motorists struggled along state roads.

The fog resulted in part from rising temperatures that caused the snow that blanketed the state to melt.

In Springfield, for example, traffic lights were stuck on one color for long periods of time because sensors perched above some intersections could not see through the thick fog to determine if vehicles were waiting.

And in the southwestern Illinois community of Worden, fog may have contributed to a crash involving a freight train and a truck shortly after 8 a.m. The Illinois State Police say the truck's driver was taken to a nearby hospital after the fiery crash, but his condition wasn't immediately available.

East of St. Louis, a stretch of eastbound Interstate 270 was closed for three hours Monday for cleanup after nine fog-related crashes involved 20 vehicles over a half-mile stretch shortly before 11 a.m., Illinois State Police Master Trooper Ralph Timmins said. Seven other vehicles drove onto the median or into ditches to avert collisions, Timmins said.

About 15 people were taken to area hospitals, but only one had injuries severe enough to require that person to be transferred by helicopter to a St. Louis hospital, state police said.

Flights at Midway were canceled until at least 4 p.m. Monday, said Gregg Cunningham, a spokesman for the Chicago's aviation department. He said O'Hare saw more than 300 flights canceled, with average delays of 45 minutes for those still taking off and landing.

The National Weather Service issued dense fog advisories for much of the state until at least Monday evening, and warned they could be extended.

The rising temperatures also brought concerns about possible ice jams on area rivers, which officials were closely monitoring to determine if dislodged ice is flowing downstream and jamming at other spots, said NWS meteorologist Stephen Rodriguez.