About 1 700 flights in and out of Chicago's airports have been cancelled in the last 24 hours amid the frigid weather in the Midwest , with experts saying the cold is affecting transit operations. The temperature on Thursday morning at O'Hare International Airport was negative 29°C. About 1 450 flights were cancelled at O'Hare, one of the nation's busiest airports.Midway International Airport had about 250 cancellations. Both airports were reporting delays of about 15 minutes.Airline experts say the double-digit subzero temperatures affect manpower, equipment and fueling at airports. United Airlines has brought in heated tents for its employees at O'Hare and added workers to increase shifts.The low temperatures also affected rail service in Chicago, the nation's third-largest city. Some commuter lines are shutting down or altering schedules amid the cold.Officials are warning Michigan residents that they risk brief interruptions of natural gas service for heat amid bitterly cold weather if they don't help reduce energy.The warning comes after a fire at a utility's suburban Detroit facility that affected natural gas supplies.Consumers Energy's CEO Patti Poppe made an appeal on Wednesday night for customers to reduce their natural gas usage. She later told The Detroit News that "localised planned curtailments: for some homes and business if demand isn't reduced".An emergency alert was sent late Wednesday to cellphones asking people to lower thermostats to 65 degrees (18 Celsius) or below through Friday.Gov. Gretchen Whitmer asked everyone to "to do your part".Chicago's good SamaritanA good Samaritan offered to pay for hotel rooms for 70 homeless people in Chicago who were camped out in tents amid the bitter cold that blanketed Chicago.The offer came after the Chicago Fire Department on Wednesday confiscated nearly 100 propane tanks given the group to keep them warm as temperatures sank to negative 20°C. The department acted after one of the donated tanks exploded.Salvation Army spokesperson Jacqueline Rachev said city officials told the organisation about their actions at the camp. The Salvation Army was about to move the people to a warming centre when the city called again and informed them of the gesture.Rachev was not sure of the identity of the good Samaritan and only knew the hotel was on the city's South Side.Temperature breaks record in northern IllinoisTemperature records have been broken in northern Illinois amid the arctic deep freeze enveloping the Midwest.The National Weather Service says the temperature on Thursday morning in Rockford hit a record-breaking negative 34°C.The previous record of negative 33°C was set on January 10, 1982. The city's records date back to 1905. Rockford is about 129km northwest of Chicago.Meteorologists say warmer weather is on the way for the weekend.Closing schools, businessesDangerously cold weather in the Midwest is closing hundreds of schools, businesses and government offices in Wisconsin and Minnesota, but students are heading back to school in the Dakotas.Two of Wisconsin's largest school districts cancelled classes again on Thursday, when morning temperatures hovered around negative 29°C. In Minnesota, where wind chill readings could reach negative 48°C, several large school districts also called off classes.The extreme cold has also sent dozens of people to hospitals in Minnesota. Hennepin Healthcare in Minneapolis says it has treated 22 patients for frostbite since Friday, including 13 admitted to the hospital.But in North Dakota, students in Fargo and other nearby cities are heading back to school. Temperatures in the region dropped to minus 31°C on Thursday morning but forecasters are predicting a high of minus 16°C.It's a bit warmer in South Dakota, where the National Weather Service says the high temperature in Sioux Falls on Thursday is expected to be minus 11°C.