Wet-bulb temperature is a measure of the lowest temperature that can be reached by evaporating water into the air at a constant pressure. It is defined as the temperature indicated by a thermometer when the bulb of the thermometer is moistened with water and exposed to airflow. This thermometer reads lower than the dry-bulb temperature (the air temperature measured by a regular thermometer) when the air is not fully saturated with moisture because of the cooling effect of the evaporation of water.
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