Feeling especially dumb lately? Hey cool, me too. According to a new study, when it's really hot outside, it makes people dumber.

The Harvard researchers found when there's a heat wave, students get lower scores on tests than they do when the weather's nicer. Specifically, they tested people in their dorms on hot days with and without air conditioning. The students without cool air performed worse on their cognitive tests.

The study also found out that on the "cool down" days following a heat wave we're still dumb. The students they tested showed 13% longer reaction times and 13% lower scores over the course of two weeks.

“Indoor temperatures often continue to rise even after outdoor temperatures subside, giving the false impression that the hazard has passed, when in fact the ‘indoor heat wave’ continues,” said Joseph Allen. “In regions of the world with predominantly cold climates, buildings were designed to retain heat. These buildings have a hard time shedding heat during hotter summer days created by the changing climate, giving rise to indoor heat waves.”

Read more at Boston Globe.