INDIANAPOLIS — Despite how it sounds, relative humidity isn’t a great measure of how humid it feels outside.
That’s why, when it’s muggy, meteorologists talk about dew point temperature instead.
Relative humidity (RH) measures how much moisture is in the air, compared to the amount of moisture the air can hold. It’s expressed as a percentage, so a 50% RH means the air is carrying half its maximum amount of moisture.
Watch below: Relative humidity demo
However, because warmer air can hold more water, the RH percentage doesn’t necessarily increase as the temperature does, even if the air is holding a much larger amount of moisture, making it feel more humid outside.
On a 65-degree spring day with a dew point temperature of 46, the relative humidity calculates out to 50%. And a 95-degree summer day with dew point of 73, relative humidity is also 50%.
As you know, those two days feel very different. The 95-degree air can hold a lot more water than 65-degree air, making it far more humid.
Coming up in ‘What in the Weather?’
Check back weekly for “What in the Weather?” questions and answers. In the coming weeks, we’ll explain some very unusual hurricane season activity, the myth of heat lightning and what causes a “fogbo.”
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