A meteorological term used to assess heat stress in direct sunlight. It takes into considerate air temperature, humidity, wind speed, sun angle and cloud cover. It combines dry air with humidity. A wet cloth is placed over the bulb of the thermometer – this lowers the temperature reading on the thermometer. When humidity is high, the wet-bulb temperature is closer to the dry-bulb temperature. It’s used to determine when outside conditions are dangerous for people to stay out in. When the air is dry sweat evaporates when the air is wet, it’s harder for sweat to evaporate, making it more dangerous to stay outside for prolonged periods of time. The wet-bulb temperature gives an indication as to whether people will be able to cool themselves by sweating. A wet-bulb calculator can be found here.