Heat waves are primarily caused by high-pressure systems that push warm air down onto an area and hold it there. During heat waves, the air is stagnant, with little wind to blow away pollutant emissions from sources like vehicles or buildings. Sunny, hot conditions also encourage ozone to form faster. As a heat wave continues, pollution builds up.

Heat doesn’t just mean canceled events. It also poses a health risk. If you can’t afford to cool the whole house, make a “cool space” to sleep in. Because experts say the best defense