The Star-Herald

Muggy or not? Look to the dew point

With summer in sight, I thought it would be a good idea to reintroduce the way that you can use the dew point as a comfort gauge.

When you want to know how muggy it is going to feel outdoors, it is the dew point, and not the relative humidity, that is the go-to number. Dew point is a stand-in, or proxy, for the actual amount of water vapor in the air, whereas relative humidity changes as the temperature changes.

The higher the dew point, the more water vapor there is in the air, and as a result, our bodies have a harder time cooling off through the evaporation of our sweat. That’s why we tend to feel sluggish on such days.

I have devised a table, in 5-degree increments, based on conversations with County folks, showing how most people feel at different dew point temperatures. Before we get to the table, let me tell you where to find the dew point.

Just Google “NWS RWR GYX” (National Weather Service Regional Weather Roundup out of the Gray, Maine, NWS office).

What you will get is a table of conditions at the top of the previous hour, with Presque Isle and Caribou near the the bottom of the list of locations you will see running down the left side of the table.

The dew point is the second column of numbers, with “DP” above it.

So now that you know how to find the dew point, how can you use it as a comfort guide?

Well, I have put together what I call the Dew Point Comfort Scale, which again, applies to folks from up here, who are, for the most part, not fans (pun intended) of muggy-feeling air.

Here is the scale:

When the dew point is below 50 degrees, most people find it to be quite comfortable.  At 50, the moisture in the air becomes noticeable. At a dew point of 55, the air begins to feel muggy for people who are quite sensitive to muggy-feeling air. At a dew point of 60, most people find that it feels muggy. At 65, most find the air very uncomfortable, and at 70, which at most will happen two or three times a summer, most people find it to be simply brutal, and in fact, you hear people talking about the weather on those days just about as much as you do on the day before a major winter storm.

Before closing, a few words about the days many of us love, those warm summer days with not a hint of mugginess. Well, on those days, the air is so dry, we don’t notice that we are sweating like we do on humid days. This is because the sweat we produce transforms almost immediately to water vapor when the surrounding air is dry. So it is easy to become dehydrated on comfortable days, since you don’t see yourself sweating, and thus it doesn’t occur to you as readily that you need to drink.

Ted Shapiro holds the Broadcast Seal of Approval from both the American Meteorological Society and the National Weather Association. An Alexandria, Va. native, he has been chief meteorologist at WAGM-TV since 2006. Email him at tshapiro@wagmtv.com.

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