Dew point: Why it’s important


SIOUX FALLS, S.D. (KELO) — Now that meteorological summer has begun, there’s one other thing to talk about: Humidity.

Meteorologist Adam Rutt explains why the dew point is so important when it comes to comfort.

During the summer, you’ll often hear us talking about humidity and whether it’s comfortable to be outside. But why do we focus on the dew point when we bring this up?

Relative humidity is the measure of how saturated the atmosphere is at a given temperature. By definition, the dew point is the temperature at which the air is completely saturated and can’t hold any more moisture. This is where comfort comes into play. Higher dew points mean more moisture can be held in the atmosphere, and vice versa.

We tend to focus on the dew point, because that is a more accurate way to show how comfortable it may be. Let’s use a “glass half-full” analogy and say that the atmosphere is like a glass of water. Cooler air temperatures are like a smaller glass, which won’t need as much water to make it half-full. Warmer days, however, are like bigger glasses of water, and bigger glasses need more water to reach 50% capacity. Simply put, more “water in the glass” means less comfort for us.

Thankfully, the dew point can never exceed the air temperature. Once we reach 100% humidity, the air can’t hold any more moisture, and it has to get rid of it… usually as rain.

While Friday and Saturday won’t be too uncomfortable, dew points climb into the mid to upper 60s by Sunday. So, get ready for some early season mugginess as we approach the second week of June.

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