Rain, snow and storms already cause about one third of all airline delays, and climate change could add another variable resulting in more delayed and cancelled flights: heat.

Forbes reports that a recent study in the journal Climatic Change said rising global temperatures could cause more weather incidents like that experienced in Phoenix, Arizona, in June, when dozens of flights were cancelled due to temperatures which rose above 118 degrees Fahrenheit (48 degrees Celsius).

Not only does high heat make it dangerous to take off due to decreased lift under the wings of aircraft, but excessive temperatures also mean less weight capacity — meaning fewer passengers and cargo, and thus higher prices.

“During the hottest parts of the day, 10 to 30 per cent of fully loaded planes may have to remove some fuel, cargo or passengers, or else wait for cooler hours to fly,” the study noted. “Weight must be dumped, or else the flight delayed or cancelled.”

Researchers said that on the hottest days, aircraft weight would need to be reduced by as much as 4 per cent. Depending on the aircraft, that could translate into 12 to 13 fewer passengers.

Average global temperatures have generally been rising, with 2016 the warmest year on record. Studies have shown an increase in heat waves, with increased incidents of high heat predicted.