The Groundhog Day Blizzard ran from January 31 through February 2, 2011. The National Weather Service measured 21.2 inches at O’Hare, the third-largest storm total in Chicago history. The heart of it was fiercer than the three-day number suggests: 20.0 inches fell in the 24 hours from the afternoon of February 1 into the morning of February 2, the city’s highest 24-hour snowfall on record. Winds gusted to 50 and 60 mph. Visibility at O’Hare stayed at or below a quarter mile for 11 hours. There was thunder and small hail mixed into the snow. Lake Shore Drive was shut down with cars stranded on it.
Only a few Chicago storms meet the formal definition of a blizzard. The Weather Service puts 1967 and 2011 in that group: sustained wind or frequent gusts of 35 mph or more, and visibility held down for a long time. The 2011 storm had the most wind of the big four.
Snow depth was not the only hazard
Drifts of several feet, and a few much larger, formed against buildings, in alleys, and across side-wall vent pipes. A high-efficiency furnace that lost its intake or exhaust in that drift shut itself off. That safety shutdown is correct. It also means a dark house and no heat while the wind is still stacking snow. Atmospheric chimneys took a different beating: wind-driven snow down an older flue, then a furnace that would not draft when someone needed it at 3 a.m.
Power outages and impassable side streets did the rest. A boiler that is off for a day in a vacant house, with the outdoor temperature in the teens and wind in the gusts, is how pipes freeze in a neighborhood that otherwise rode the storm out. The city was better prepared than it had been in 1967. Forecasts were good, and the main routes were cleared faster. Side streets and private drives were still a multi-day problem, which is the scale a heating emergency has to survive.
What to take from it
Know where the furnace or boiler vents terminate, and whether a five-foot drift would cover them. Have the system serviced before February, including a check that it restarts after a power blink. If you travel in winter, leave the heat at a steady set point rather than off. A failed igniter on February 1, 2011, was not a same-day repair for a lot of people.
Zima HVAC is in Mundelein, which sat under the same storm. Call (847) 323-8314 for a midwinter check if this season’s first snow already exposed a weak restart or a buried vent. The longer history of the record storm is in our piece on the blizzard of 1967.