What Does Humidity Mean?
Updated 2026-01-10
What humidity actually measures
The humidity percentage shown in a weather forecast is relative humidity: the amount of water vapor currently in the air compared to the maximum amount the air could hold at that temperature. Warm air can hold far more moisture than cold air, so the same amount of water vapor produces a much higher relative humidity reading on a cold day than on a hot one.
Why humidity affects how hot it feels
Humidity matters because it affects how efficiently your body can cool itself. Sweat cools you down as it evaporates, but in high humidity the air is already close to saturated, so sweat evaporates more slowly and you feel hotter than the air temperature alone would suggest. This is why "feels like" temperatures climb sharply on hot, humid days even when the actual thermometer reading hasn't changed.
Typical comfortable ranges
Most people find humidity between roughly 30% and 50% comfortable at typical indoor and outdoor temperatures. Above about 60%, the air can start to feel sticky or heavy, and prolonged exposure to high heat and high humidity together raises the risk of heat-related illness, since the body's main cooling mechanism becomes less effective.