Dallas County area schools closed Monday with delays on Tuesday due to below freezing temperatures caused by a "polar vortex." The arctic air didn’t just hit Iowa; almost two-thirds of the U.S. was affected causing delays, traffic accidents and even some power outages in its wake.

Delays and school cancellations were more common in Iowa including those at Waukee.

Waukee Superintendent Dr. David Wilkerson said the decision to cancel school Monday was a "no brainer" and a second cancellation Tuesday was based on buses being unable to start.

"Our decision not to have school was based solely on the fact that as of late (Monday) afternoon/evening we still had 19 of our 60 buses that would not start due to the harsh conditions," he said. Buses at Adel-DeSoto-Minburn were operational Monday, but Superintendent Greg Dufoe said the decision to cancel school was based on the extreme wind chill.

"The decision to cancel school became easy when the forecast called for wind chills so low that it could cause frostbite," he said. "We didn’t feel like we could put kids out in that weather if they were walking, driving or riding the bus to school."

A-D-M Community Schools, along with other area schools, re-opened Tuesday after a two-hour delay.

"A lot of discussion was held on whether we should close, but as we moved through Monday the forecast for Tuesday improved and the warning for windchills downgraded so we felt a two-hour delay was adequate."

District schools including A-D-M will now make up the missed day at the end of the year, pushing students’ last day to May 23.

Although area students will have an extra day to make up at the end of the year, Dallas Center-Grimes Superintendent Scott Grimes said student safety is their number one concern.

"I would say the first and foremost reason is for student safety," he said. "Whether that be with inclement weather where roadways can become dangerous to travel on. We also not only need to take into account whether buses can travel, but need to consider young drivers as well." And, at the start or end of the day, traffic is going to be heavy in and around the school district, added Dufoe.

When winter weather hits there is no standard or science to closing school versus a delay. Superintendents have to make the call at a local level instead.

"Superintendents from around the state make the call at the local level purely from a safety perspective," Wilkerson said. "As you can imagine that varies greatly from one district to another and across the state."

Woodward-Granger Superintendent Brad Anderson said he relies on a "tight network of local school superintendents to talk through each scenario and bounce ideas off of one another prior to making any decision. In addition, we have contacts with the National and Local Weather Service to help shed some light on the potential threatening conditions."

And that networking extends to other sources, said Wilkerson. "We consult with our city street crews as well as our snow removal vendors," he said. "Often times we’ll check weather radar, and sometimes the local weather stations. Sometimes an hour or two delay is all that is needed to get roads opened up or to provide daylight so that visibility improves for our drivers."

That’s especially important in Dallas County, with a high rural component, school officials agree. "DC-G needs to always treat Highway 44 between Dallas Center and Grimes with respect as it can drift and ice over in parts due to the northerly winds," Grimes said.

Likewise, for a Woodward-Granger student in Jester park, on the eastern edge of the district, it’s a 20-mile commute to Woodward along a wind-swept Highway 141.

Each district takes into consideration factors such as the danger of students walking to school due to low temperatures and the possibility of buses breaking down each time winter weather hits.

"Each comes with its own set of stresses," Anderson said. "In closing early you worry about everyone getting home safely and whether or not the timing of everything is best and with closing the decision is always questioned as nobody wants to make up the day when it’s nice outside," Dufoe concurred, saying each scenario presents its own set of challenges.