Teachers in Hawaii say their classrooms are so hot they are sending students to the nurse with symptoms of heat exhaustion.

Unbearably hot classrooms have prompted school officials to consider having "heat days" — like snow days — to cancel school when it's too hot to learn.

More than 90 percent of Hawaii's schools don't have air conditioning.

The lack of air conditioning comes during a particularly scorching year for the state. The National Weather Service says Honolulu temperatures reached record highs at least 25 times in the last year. And experts say Hawaii's cooling trade winds have been declining for decades.

The state Department of Education says it would cost $1.7 billion to install air conditioning in all Hawaii schools. A spokeswoman for the department says officials are open to considering heat days.