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“It’s not the heat, it’s the humidity.”

That’s mostly true. But dew point is actually a better indicator of how comfortable we feel in any given air mass.

This week’s air mass over Minnesota feels delightful. That’s not just because temperatures are in the 60s and 70s. 

Dew points this week in Minnesota are in the very comfortable 30s and 40s. 

That means there’s less than half the amount of water vapor in the atmosphere than in tropical air masses when dew points hover around 70 degrees.

A note about using humidity as a comfort guide. What we call humidity is actually relative humidity. It’s relative compared to the air temperatures at any given time. Dew point is an absolute measure of moisture in the atmosphere, thus a better indicator of comfort. Relative humidity can vary greatly throughout the day, even though the dew point stays the same. 

Here’s an example. The relative humidity at Minneapolis-St. Paul International Airport at 2:53 a.m. Wednesday morning was 81 percent. The temperature was 58 degrees and the dew point was 50 degrees.

At 9:53 a.m., the relative humidity dropped to 53 percent as the temperature rose to 68 degrees. But the dew point remained at 50 degrees. That means there was still the 

 as at 2:53 a.m. when the humidity was 81 percent!

So when you want to gauge the comfort of a summer air mass in Minnesota it’s usually better to use the dew point. It’s a better measure of just how much moisture is in the air at any given time. 

Weather and Climate News

Updraft® - Minnesota Weather News

Paul Huttner

Author

Dew points tell us how comfortable we feel in any given air mass. 

It's not the heat, it's the dew point!

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