CHICAGO (CBS) — The Chicago Public Schools will close for a second day on Tuesday due to the extreme cold.

CPS CEO Barbara Byrd Bennett made the announcement at a news conference on Tuesday afternoon.

Temperatures are expected to be well below zero on Tuesday morning, with wind chills around 30 below.

The district, which has 400,000 students, said it will be contacting parents via robo-calls and email.

Closing of Chicago schools is extremely rare.

The Chicago Public Schools system last called for a district-wide closing after the blizzard of Feb. 2, 2011; before that it was in January 1999.

Over the weekend, the city had planned to keep schools open on Monday, but offer parents the option to keep their children at home with an excused absence.

On Sunday afternoon, following a campaign by the teachers’ union, CPS decided to close schools on Monday.

At the news conference on Tuesday, Bennett said the union’s public push to close schools did not affect her decision.

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