Public schools were open Monday ahead of what Mayor Bill de Blasio called potentially "the biggest snowstorm in the history of New York City." The city did cancel all after-school activities, field trips, youth sports programs and adult education classes scheduled for Monday, the New York Post reported. De Blasio said he expected to close schools Tuesday.

Forecasters predicted the major storm would slam the Northeast starting Monday afternoon and continue into Tuesday. The National Weather Service issued a blizzard warning for the New York City area from 1 p.m. Monday to midnight Tuesday. NYC could see up to 3 feet of snow and gusts of wind up to 55 mph, according to the warning.

Complicating school cancellations were the state’s regents exams, which were scheduled to start Monday in high schools. Students must pass five regents exams to graduate, and this year’s January tests were due to go through Thursday.

The state forbids schools from giving regents under extreme circumstances. Schools may not administer state exams when weather conditions are severe enough to warrant closing school and canceling normal bus transportation,” according to New York policy. The next round of regents is set for June 16-25.

Higher education officials also considered how to best respond to the blizzard warning Monday. New York University was open but “very closely monitoring the progress of the impending snowstorm,” according to its website. Columbia University hadn't canceled classes Monday, either.

Dowling College and Farmingdale State College, both in Long Island, were closed Monday. St. John’s University in Queens canceled classes at all of its campuses, and Wagner College in Staten Island planned to suspend all activity after 2:30 p.m.

Some private schools and institutions located near New York City had already shut their doors Monday morning. NBC reported 227 school closings or early dismissals in the area. See the full list here.