One twisted thing about cooling and climate change: It’s all a vicious cycle. As temperatures rise, the need for cooling technologies increases. In turn, more fossil-fuel power plants are firing up to meet that demand, turning up the temperature of the planet in the process.

“Cooling degree days” are one measure of the need for additional cooling. Basically, you take a preset baseline temperature and figure out how much the temperature exceeds it. Say the baseline (above which you’d likely need to flip on a cooling device) is 21 °C (70 °F). If the average temperature for a day is 26 °C, that’s five cooling degree days on a single day. Repeat that every day for a month, and you wind up with 150 cooling degree days.