Many of Michigan's public schools were closed for three days during the Polar Vortex last week.
This brings them close to the state's annual limit of five or six calamity days.
The number of days varies among school districts depending on the length of their school days and of their school year.
Michigan requires schools to offer 170 days of instruction and 1,098 hours of classes.
Grand Rapids Public Schools spokesperson John Helmholdt said if schools go over their limit of calamity days, they can choose how to make up lost days.
"They have the option of either adding a day or two or however many days are necessary at the end of the school year, Helmholdt said. "Or what they can do is simply extend the length of the school day for the remaining part of the school year."
Mike Shibler is superintendent of Rockford Public Schools. He said generally families prefer time be added to the school day. This is because extending the length of the school year can interfere with summer plans.
Shibler said if a district does not make up lost time after going over its limit, the penalty is a loss of some state aid. "If they lost two days and didn't make them up, they'd lose those two days of funding. And quite frankly that's why it's such an important issue because there isn't any district in the state that can afford to lose any funding."
Shibler said that on Jan. 6, the state government closed down along with almost all of Michigan's school districts. So he anticipates that Gov. Snyder will consider giving Jan. 6 as a grace day. That would mean schools would have one less snow day to count.
Shibler said that school closure decisions are always based on protecting student safety.
Virginia Gordan, Michigan Radio Newsroom