As students return to classrooms, record-breaking temperatures amid a late-summer heat wave are causing schools across the Mid-Atlantic and Northeast to either close or dismiss students early this week.

The National Weather Service warned Tuesday that a heat wave will "persist in the Mid-Atlantic and Northeast through Thursday and linger all week in Texas and neighboring states." Scorching weather is expected through the week from Texas into the Upper Midwest, and into the Mid-Atlantic and Northeast with temperatures rising more than 10 degrees above normal, according to the weather service.

As of Tuesday, more than 61 million people were under heat advisories in parts of the country, bringing some heat to this year's back-to-school season. School districts in several states — including New Jersey, Pennsylvania and Michigan — are planning to modify their schedules by closing or dismissing students early.

The disruptions follow similar decisions made by other districts across the country in late August when a sweltering heat dome blanketed the Midwest and Gulf region. Broken or nonexistent cooling systems at schools in Illinois, Indiana, Iowa, Missouri, Ohio, Wisconsin, and other states were forced to close or dismiss students early to deal with the heat.

The weather service at the time called temperatures "extremely anomalous" as some regions climbed into the triple-digits.

While school closures due to excessive heat aren't new, educators have said they are becoming more common as climate change causes more severe weather.

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Thousands of schools without adequate HVAC systems

Experts have urged schools to address the issue of hotter classrooms and concerns over how extreme heat can affect students. Rising temperatures have also raised issues over funding as school districts face millions in added costs to install, upgrade, operate, and maintain heating, ventilation, and air conditioning systems, according to a 2021 report from the Center for Climate Integrity.

The report noted that more than 13,700 K-12 public schools that didn't need cooling systems in 1970 will need them by 2025, at a cost of $40 billion. More than 13,000 additional schools will need to upgrade their existing cooling systems to keep up with increased cooling capacities, which will cost more than $414 million.

Some schools struggle to install cooling systems

In Ohio, Canton-area schools closed Tuesday due to the extreme heat. Heritage Christian Academy Superintendent Sharla Elton told the Massillon Independent, part of the USA TODAY Network, that closures are always a difficult decision but sometimes unavoidable.

"We want kids in school and learning, but if it is not going to be a comfortable learning environment we have to weigh the decision," Elton said.

Heritage Christian's four-story building, which was built nearly 100 years ago, has limited air conditioning, according to Elton. There is no AC in classrooms or common areas.

A project is underway to add air conditioning to the common areas, including the library, cafeteria, auditorium, and STEAM and computer labs. The $250,000 project is expected to be completed in the spring.

But unlike Heritage Christian, public schools across the nation struggle to find the funding to install or upgrade their cooling systems.

Shain Bergan, a spokesperson for Kansas City Public Schools in Missouri, previously told USA TODAY that not all classrooms are cool despite all of the district's buildings having some form of a cooling system. He added the district has tried and failed to pass a bond referendum to install central air.

In Wisconsin, educators expressed their disappointment over the shortfall of public schools’ budgets when Gov. Tony Evers greeted Milwaukee students on their first day of school on Tuesday. Only a few hours after students were dropped off, Milwaukee Public Schools closed classrooms for the afternoon because of the heat.

Most of the district's buildings lack air conditioning. 

A similar heat wave has caused closures in the school district in 2021. At the time, Superintendent Keith Posley said air conditioning would be a priority in the district's pandemic relief funding. But estimates put costs at about $1.5 million and $2.5 million per building.

Since then, air conditioning proposals and projects have either been voted down or rejected. Milwaukee School Board Vice President Jilly Gokalgandhi said it's a challenge with a tight budget, and the district would need to establish an equitable system for choosing which buildings would get it first.

Contributing: Krystal Nurse and Tiffany Cusaac-Smith, USA TODAY; Amy L. Knapp, Massillon Independent; Rory Linnane, Milwaukee Journal Sentinel