I just went back to this website today, and it shows 84 F dewpoint again in Clarion while the surrounding weather stations show 73 – 79 F dewpoints. I believe the 73 F dewpoints, but I am not sure about the 79 F dewpoint either. My only point is that one should be careful when using other people’s data. I doubt that the guy at the airport in Clarion (population 2800) calibrates his sensors too often. Since this station is also showing an 84 F dry-bulb temperature (100% RH), I wouldn’t be surprised if he is using a wet-bulb thermometer for humidity and hasn’t wetted his wick in quite a while.

It’s good to be skeptical, Roy. I just went to see if they said anything about where the data come from and noticed that they give the weather station for each entry when you go to the state level. I didn’t look at the state level last week, but the area where that 84° F dew point was showing seems like it might have been Clarion, with weather station KCAV.

I am still skeptical of that dewpoint map website. I think some of their sensors need calibration. I am guessing that this data is coming from internet-connected home weather stations.

An interesting discussion in your article! The diurnal swings aren’t (or shouldn’t be) surprising, but the degree of stratification within such a short space surprised me. However, as the comments suggest, a great deal of interplay is likely with the roof above. Are you aware of (yes, I will have to pull out my own Google-fu) any studies showing humidity strata in the open air?
Can’t say I really know where I’m going with this topic, really just reaching for a better grasp on understanding conditions before hoping to manipulate them.
Cheers

Matt, I’ll be replacing mine, but I’ve got a number of things to do first. All the improvements I have planned are one reason I undersized my mini-split heat pumps. It’ll sure be nice to get to the windows, though.

Daphne, yes, humidity does stratify. I’ve measure significant differences in relative humidity and dew point from the floor to the ridge in encapsulated attics (link below). The water molecule is lighter than nitrogen and oxygen molecules, but I think there’s more to it than that.

Humidity in a Spray Foam Attic

Roy, if you click on the last link in the Related Articles section, you’ll see that the record dew point for the US is 91° F. That was Melbourne, Florida, not a surprise. Also not a surprise is that New Orleans is tied for second at 90° F. And so is Appleton, Wisconsin. The upper Midwest can get some nasty humidity sometimes.

When I looked at the map, most of Iowas was in the 70s Fahrenheit, but there was one place in north central Iowa that stuck out at 84° F. You must have been in one of the other parts of the state or maybe at a time when it was less humid.