Baltimore County will close 37 schools today, and perhaps early next week, under a recently adopted policy requiring schools without air conditioning to be closed when the heat index is forecast to reach at least 90 degrees.

The new policy, adopted this month, is being applied just two days after the start of the new school year. It removes the superintendent's discretion to decide when to close schools and requires him to announce school closures by 8 p.m. the night before a forecast of a high heat index.

“It could be that students might not have school at all next week,” said Superintendent Dallas Dance. “That could be a problem.”

Not only might students miss school, but all sports and after-school activities at those schools would be canceled as well. The rest of the county's 173 schools have air conditioning and will remain open.

The National Weather Service is forecasting temperatures in the lower 90s and high humidity by early this afternoon. That translates to a heat index of 98 or 99 degrees, according to the weather service.

Late-summer heat is expected to continue into next week, with temperatures around 90 degrees and an even higher heat index forecast through the first three days of the week. Had the policy been in effect during the last school year, schools without air conditioning might have closed twice in August, six times in September and twice in May.

Dance said he would seek a waiver from the Maryland State Department of Education requirement that students be in school for 180 days, if more heat-related closures occur. Under such a waiver, students at the affected schools would not have to make up the missed days later in the school year.

Parents are divided over whether heat-related closures are good for students.

Lily Rowe, a parent who advocated for the policy, believes it is inhumane for children to be stuck in hot classrooms.

She said the schools should have been closed Thursday as well after the forecast showed a 90-degree heat index for Dundalk by 8 p.m. the night before.

“I am angry about it,” she said. “Now the superintendent's office isn't following the heat closure policy.”

Rowe and other parents posted pictures of the forecasts on social media with angry comments about Dance not closing schools.

Other parents disagreed.

“How can my child grow intellectually, socially when she is at home?” said Jennifer Tarr, the parent of a junior at Dulaney High School. “She needs to be in school. Yes, it is uncomfortable.”

Tarr is more concerned about overcrowding at the school, and the aging building and old pipes, than the heat during September.

“I question the motive of some parents,” Tarr said.

April Todd, the parent of a senior at Patapsco High School, agreed with Tarr. She would prefer school start after Labor Day when temperatures may be cooler, but she doesn't believe 90 degrees should trigger a closure.

“To me, 90 degrees is not that bad. I don't think that is warm enough to close. If it is 100 degrees that is another thing,” Todd said.

The new heat closure policy came after a group of activist parents lobbied for the change. They sought closing decisions by 8 p.m., so parents could make arrangements for the care of their children.

Many of them had worked with state Comptroller Peter Franchot in his unsuccessful attempt to get window units installed in the schools without air conditioning.

Baltimore County Executive Kevin Kamenetz refused to install window units, saying it was a waste of money to buy them and rewire schools to accommodate the added electrical load at the same time the county was close to providing a permanent solution.

The county schools had a plan to install air conditioning in all the schools. Kamenetz is accelerating the work by providing $85 million to the county schools budget. All but 11 schools will be air-conditioned by next fall, and every school but one, Colgate Elementary, which is being replaced in 2020, will have air conditioning by 2019.

The county expects the state to reimburse it for part of the costs.

Kamenetz was not involved in developing the heat policy, said Don Mohler, his chief of staff and spokesman.

“He deferred to the board to make a decision,” Mohler said.

Franchot has been monitoring the implementation of the heat closure policies “for informational purposes,” said Alan Brody, his spokesman.

In the region, only Baltimore County and Baltimore City have schools that are not air-conditioned. In the city, where many schools lack air conditioning, classes begin Monday. School closures are made at the discretion of the city schools CEO.

Baltimore Sun reporters Scott Dance and Pamela Wood contributed to this article.

liz.bowie@baltsun.com