Warmer nights could lead to poorer sleep, especially for those without air conditioning, reports USA Today.

In October 2015, an unusual heat wave hit San Diego, where not everyone has air conditioning. Obradovich and his colleague Robyn Migliorini noticed “friends and colleagues in grad school weren’t sleeping well at night — sheets off, tossing and turning in the heat — and as a result people were lethargic and somewhat grumpy,” he said. “It was pretty unpleasant.”

Spurred on by that experience, Obradovich found no one had studied sleep disruptions as a potential impact of climate change.

Researchers collected sleep data from 765,000 U.S. residents and compared the nights they reported trouble sleeping to temperature data from the National Oceanic and Atmospheric Administration. They found that unusually warm temperatures led to three nights of poor sleep per 100 people per month.

Read more at www.usatoday.com