What is the difference between Dew Point & Relative Humidty?

Relative humidity is the ratio of the water vapor in the air compared to the water vapor needed to put into the air to achieve complete saturation. Dew point is the temperature at which water condenses and is a combination of relative humidity and temperature. At a constant dew point when the temperature goes up the relative humidity goes down. Likewise, when the temperature goes down the relative humidity goes up. This explains why in the summer we see the highest humidity levels in the early morning or late evening. As the sun comes up and the air temperature begins to rise the relative humidity will drop.

Just knowing the humidity in percentage doesn’t tell the whole story because it’s relative to the actual air temperature. Warmer air can hold more moisture than cool air. The higher the dew point the more uncomfortable it feels. For this reason, dew point is a better indicator of how “sticky” it is outside compared to relative humidity.

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