CHICAGO (CBS) — Chicago Public Schools classes have been canceled for Wednesday–for the first time since 1999–as the Blizzard of 2011 blows into Chicago.

Mayor Richard Daley made the announcement at a news conference on Tuesday afternoon. More than 400,000 students are enrolled in the system.

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Given the sheer size of this storm, Daley and CPS Chief Executive Officer Terry Mazany cited the safety of students as the key reason for the rare decision to shut the school system.

“Based on the anticipation of very severe and dangerous weather conditions that could be harmful to students and their commute and their routine school day, we cannot compromise and risk their safety. Therefore we’ve decided to cancel school for tomorrow,” Mazany said.

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The City Colleges of Chicago will also be closed on Wednesday.

Earlier Tuesday, the public schools called off all after-school programs, including elementary and high school sports and driver’s education, for Tuesday and Wednesday, according to a news release. Third-shift pre-school programs and CPS programs at Chicago Park District facilities were also canceled for the day.

Special education students were dismissed early on Tuesday, but all other students left at their regular time.

MORE NEWS: Chicago Weather: Cool Down In Effect