Humidity

 

I think about humidity because my skin gets itchy when it’s too dry outside.

 

We get up in the morning here, it’s warm outside, and the thermometer looks like this; 73 degrees and 99% humidity.

My skin is happy.

 

A cold front comes through, the wind picks up from the north, and the thermometer looks like this in the morning.

Not nearly so warm, and low humidity.  I notice the difference.

 

The cold weather passes, the air flow shifts back from the southeast, from the Gulf, and the thermometer reads like this again.  High humidity.

 

Even in the cooler weather, in the middle picture, the humidity is still at 32% though, so why do I feel so dry?  32%, that’s still a lot of moisture, right?  I think the problem is that my skin is probably reacting to absolute humidity, not relative humidity, which is what the thermometer reads.

 

Relative humidity is a measure of how saturated the air is at a given temperature.  (Not that it’s actually air holding moisture, it’s really a measure of how much moisture can occupy a given space.  It can be moist inside a container, even if there is no “air” in the container, i.e. a vacuum.)  The lower the temperature though, the less moisture the air can hold.  So if you look outside in the morning and the humidity is high, take a look at where you are as well.  If you’re in South Texas, and the air is warm, it will probably feel humid.  If you’re in Colorado in the winter, and it’s 10 degrees outside, you’re going to be dry even if the humidity is at 100%!