How do meteorologists forecast a heat wave?

Heat waves often develop under a stationary high-pressure system that traps sinking air, suppresses clouds and allows the ground to heat up strongly. Forecasters use satellite data, weather stations and computer models to predict where the hot air mass will move and how long it will stay in place. Dry soils can make heat waves worse because less energy goes into evaporation and more goes into heating the air. Forecasts also consider humidity, which affects how dangerous the heat will feel to people and animals.