The Skinny about Dew Point

When meteorologists talk about current conditions, they mention temperature, heat index, winds, humidity, and dew point, amongst other things. Humidity, temperature, heat index, and winds are pretty easy to understand. Dew point, however, is rarely talked about or defined for anybody who is not obsessed with weather. So what exactly is the dew point, anyway?

According to the National Weather Service, the dew point is a measure of atmospheric moisture. This is related to humidity, as that is almost the same definition the National Weather Service gives for that term. The difference between humidity and dew point is that humidity is measured in a percentage while dew point is measured in degrees. The dew point temperature is the actual temperature that the air needs to reach in order to be completely saturated. In other words, the dew point is the temperature needed to reach 100% humidity. It is the temperature needed for condensation to form at the surface. Fog and dew in the mornings are often formed because the air temperature equals the dew point.

Dew point can be complicated to explain at times and can be confusing to understand. It isn’t a very common measured value that is talked about often. The short and easy definition to remember is that dew point is the temperature needed for 100% saturation in the atmosphere. Rain, fog, or dew doesn’t necessarily form every time the temperature and dew point are the same temperature. It is one factor that helps a lot in the process.

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