An empty classroom at City Springs Elementary/Middle School in Baltimore on Tuesday. City Springs is one of the schools having to adjust their hours due to excessively hot weather.
CNN  — 

An intense, late-summer heat wave is putting pressure on schools, students and the education system this week as temperatures climbed into the triple digits in parts of the Northeast and Midwest — record-breaking highs for early September in some places.

Heat is affecting classrooms more than in the past as the planet warms and temperatures creep higher at the beginning and end of summer, pushing dangerous heat into the school year.

This pressure is especially high at schools that don’t have reliable air conditioning, and many districts this week are canceling classes, adjusting schedules and forgoing after-school activities to keep kids out of hot classrooms.

Heat days could become the new snow days as global temperatures rise and summer gets longer. Schools now need to prepare for extremes on both ends of the spectrum, said Kevin Lanza, an assistant professor at UTHealth Houston School of Public Health.

“There will be higher numbers of days with extreme heat into the future and they will start trickling into what we consider the typical school year,” Lanza told CNN.

Heat isn’t just a health risk – it also challenges learning: A 2018 study from the Harvard Kennedy School showed that in schools without AC, students learning over the course of the year dropped 1% for every 1-degree Fahrenheit increase in temperature.

Schools are not equipped to deal with the extreme weather they face, said Laura Schifter, a senior fellow at the non-profit think tank Aspen Institute and lead of This is Planet Ed.

“Schools really need to be thinking about how climate change is going to impact them and how they can develop and build plans in place to adequately respond,” Schifter told CNN.

‘They can’t learn in the heat’

Patricia Burton walked in the scorching hot sun on Tuesday to pick up her 9-year-old son, Delano, after he was dismissed from City Springs Elementary School in Baltimore three hours earlier than usual. Burton told CNN she worries about her son’s well-being, knowing that outside temperatures are blistering, and the school does not have adequate air conditioning.

Most of all, she worries because Delano has asthma.

“I worry about everybody’s kids that go here, because it’s not just mine, it’s all of our babies that’s in this heat,” Burton said. “Why not give them air? Why not help them want to come and be productive and do what they need to do to learn? They can’t learn in the heat.”

“That’s a lot on them and the teachers,” she added.

City Springs Elementary/Middle School in Baltimore is one of the schools adjusting their schedule due to hot weather.

Baltimore temperatures could hit 101 degrees on Wednesday, the National Weather Service says. It has only climbed to 100 degrees three other times since 1872 — and it could happen twice this week.

Baltimore City Public Schools — including Delano’s — announced early dismissal for multiple locations without air conditioning on Tuesday and Wednesday.

Schools in the Midwest, including in Milwaukee, Chicago and Detroit, also changed schedules this week or closed due to punishing heat. And Philadelphia is facing four consecutive days with temperatures over 95 degrees Fahrenheit, which has never happened during the month of September in the records dating back to 1873.

In a letter sent to family members, the School District of Philadelphia announced that dozens of schools “without air conditioning” or with “inadequate cooling” would be dismissed three hours early on Tuesday and Wednesday.

“We have been working with urgency over the past five years to install updated air conditioning systems and the extensive electrical systems that support them in our schools,” Oz Hill, chief operations officer for the school district, wrote in the letter. “We will continue to expedite this work … in order to eliminate extreme heat as a disruption to in-person learning.”

Cooling units are brought to a Baltimore school.

While climate change is a major contributor to these school disruptions, experts tell CNN another reason is that many of the country’s school buildings are “outdated” and were built in a climate that was considerably different.

“There are a lot of challenges to just updating these school buildings and making them function to the increased heat that we have now,” Schifter said. “It’s not as simple as just throwing an air conditioning unit on a building if the building itself is not built to withstand the climate that it exists in today.”

In some states, community advocates have launched campaigns to help make schools healthier and safer for students and teachers even as the climate crisis worsens, while also helping them break their reliance on fossil fuel energy. Some solutions include changing heat-trapping asphalt in playgrounds to green spaces with more shade or installing heat pumps, instead of traditional fossil fuel-powered air conditioners to cool buildings.

“This is where you have to shift resources to this problem, whether that’s within that region or at the federal level,” Lanza said. “Learning in an environment that has safe and comfortable temperatures should be a certain type of human right, and I think that we’re not meeting that with our current setup.”

CNN’s Brandon Miller and Amy Simonson contributed to this report.