One of the most precious rituals for a student in the Northeast is to peer out the window on a winter morning, witness a flurry of snow, and realize that there’s no need to cram for that test — snow day!

But “heat days” might soon become just as regular an occurrence. With extreme temperatures blanketing towns in New Jersey, Connecticut and New York this week, schools in dozens of districts across the region where air conditioning is not always the norm closed early or canceled after-school activities.

On Thursday, as temperatures climbed above 90, more than two dozen New Jersey districts dismissed students early. Dozens of schools in Connecticut, including those in West Haven, Milford, Naugatuck, Waterbury, Bristol and Farmington, did the same. And in New York, at least two districts closed schools early, with a number of others canceling after-school sports.