More than 150 people fell ill in the stifling heat at a high-school graduation ceremony in Paterson, NJ — where the city’s mayor declared a state of emergency Tuesday after the “mass casualty event.”

Dozens of graduation attendees had to be treated at the event, officials said.

At least five people were hospitalized for dehydration as students’ family and friends lined up outside Hinchliffe Stadium on Monday morning, Paterson Public Safety Director Jerry Speziale told CBS New York.

While students and guests were left sitting in the sweltering sun, school officials, including Board of Education members, were seated under tents, according to NorthJersey.com. The Paterson School District did not respond immediately to a Post request for comment.

But the district insisted to the Jersey outlet that measures to keep parents, students and staff safe were in place at the time.

“In anticipation of high temperatures, the district implemented numerous precautionary measures to help keep everyone safe,” Paterson School District Superintendent Laurie Newell told NorthJersey.com in a statement.

“These included on-site EMTs, multiple cooling stations, cold bottled water, shaded areas, wet paper towels, ice, and large industrial fans to provide airflow.”

One graduation parent had to be treated in an ambulance after suffering an asthma attack as temperatures soared into the high 90s.

“They gave me the breathing machine,” said the woman, who didn’t give her name. “They wanted to take me [to the hospital], but I didn’t want to go because I didn’t want to miss my son’s graduation.”

As a result of the “mass casualty event,” proactive measures have been taken in the city until the heat wave ends, hopefully by Wednesday night, Paterson officials said.

“Due to the extreme heat, I declared a state of emergency yesterday in our city. All recreational activities are canceled until further notice,” Paterson Mayor André Sayegh said in a social media post Tuesday.

Temporary cooling stations also have been set up in Paterson libraries between 9 a.m. and 5 p.m. “offering air-conditioned relief and water,” according to the Paterson Police Department.

Much of New Jersey, New York and Connecticut were also under excessive heat warnings Tuesday as temperatures in Manhattan topped 100 degrees.

An air quality alert was issued across much of the area due to ground-level ozone.