A resident shovels snow in Ann Arbor on Friday, Jan. 25. A snow, sleet and freezing rain mixture Jan. 27 through the night led to the first snow day in 2 years for Washtenaw County students.

Daniel Brenner I AnnArbor.com file photo

• Related: Icy conditions prompt school closings across Washtenaw County
• Related: Multiple accidents reported on icy roadways Monday morning Related: Weather causes Ann Arbor Public Schools to cancel all athletic events and practices, other districts varied

A messy mix of overnight snow, sleet and freezing rain gave Ann Arbor-area students their first snow day in two years.

The winter of 2011-12 was the fifth warmest on record in the Ann Arbor area, resulting in no extra days off for students. Washtenaw Intermediate School District Superintendent Scott Menzel said it was the first year in his 10 years as a superintendent that there were no snow days.

More than 400 school closings were reported in southeast Michigan Monday as result of the conglomeration of precipitation that fell Sunday night and early Monday. All of Washtenaw County's school districts closed, as well as most of the private and charter schools.

Road conditions had improved by the time commuters got in their cars for the morning drive. But school districts have to make decisions on whether to close by 5 a.m., officials said.

Ann Arbor Public Schools leaders prefer to make the call by 4:30 a.m. to allow for parents and staff to be notified by 5 a.m., said district spokeswoman Liz Margolis.

Bus drivers report for work around that time and some bus runs start as early as 5:30 a.m., Menzel said.

The process of making the decision to close schools starts much earlier. The districts all vary slightly on their protocols, but most start the process between 1 a.m. and 3 a.m., officials said.

The WISD transportation supervisors take the lead. The WISD provides transportation for Ann Arbor, Ypsilanti and Willow Run schools.

"They're out driving the rural routes and select city routes, too, on nights like last night," Margolis said. "There are predetermined roads that they know there can be issues with. … At the district level, we have our facilities people out at the schools starting at about (2 a.m.), too, clearing snow and assessing what the ice situation is."

She said the roads on the west side of the Ann Arbor school district usually are the worst for AAPS.

The remaining districts send their own transportation officials out on the roads.

Margolis said because the district has so many more students walking these days, because of cuts to the transportation budget, the amount of ice on the sidewalks is very important to consider.

The decision to close is collaborative, school officials said. The county superintendents and transportation officials talk to one another frequently in the early hours before making a decision. There have been a number of occasions when some of the districts close and others don't, however, Margolis said.

Even though weather forecasters indicated temperatures were expected to rise to 40 degrees by mid-morning Monday, there is a general practice among county school districts not to close for a partial day, either through a late start or a "two-hour delay," Menzel said.

He said this practice was driven by feedback from parents who said a two-hour delay disrupts their work schedule.

"The preference was to either have students go or not go so (parents) could make definitive decisions," Menzel said, adding that often two-hour delays can turn into full-day closures when weather conditions don't improve as expected.

Danielle Arndt covers K-12 education for AnnArbor.com. Follow her on Twitter @DanielleArndt or email her at daniellearndt@annarbor.com.