12/08/2013 02:33 pm ET

Deep Freeze Heads For Chicago As Sub-Zero Windchill, Temperatures Expected

In a dramatic swing from last week's spring-like feel of days pushing 60 degrees, temps in the Chicago area are expected to plummet to unseasonably cold levels.

Snow was forecast for Sunday afternoon, with extra-cold wind pushing the week's already cold temps even lower. According to the Sun-Times, the wind chill could drop to as low as 15 below zero in some areas by Tuesday.

The coming week will average temperatures in the 20s with highs in only the 30s -- a good 10 degrees lower than average mid-December temps. The mercury in Chicago isn't expected to crack freezing until Thursday, according to the Tribune.

ABC Chicago reports colder-than-normal temps didn't do much to deter shoppers in Chicago's busy State Street and Michigan Avenue shopping districts. Meanwhile, the cold drove hundreds to the city's warming centers in search of shelter from the bitter temps.

According to NBC Chicago, the city's warming shelters filled up quickly by Saturday, with more than 800 people seeking shelter at the Pacific Garden Mission on the Near South Side.

"They start to increase during these times when the cold weather comes about in the city and we have to be prepared for that each night," Pacific Garden Mission Supervisor Renard Green told NBC.

Temps didn't drop below zero a single time last year in Chicago, with the lowest measured temperature of 2012 registering at 5 degrees, according to the National Weather Service.