- Part 1 of My Series: “What You May Have Missed in School.”
If you just read the words “Dew Point” and assumed it’s the time of day you can finally crack open a Mountain Dew, you are wrong. You should never reach that point of day. I’m talking about that confusing number you always ignore when you’re looking at the day’s humidity, the thing that looks like temperature, but isn’t.
Quick lesson: If the humidity is low but the dew point is high, regardless of the temperature you will probably be miserable. If the humidity is high but the dew point is low, you should plan for mugginess but not sweat-through-your-clothes-oh-my-gosh-why-am-I-out-here mugginess.
Humidity is great at telling you how much moisture is in the air at any given time, but it’s really the dew point’s relationship to the temperature that makes or breaks it all. If you plan on going outside and need to know how muggy it’s going to feel, what you really want to do to is compare the dew point, humidity, and temperature (never forget temperature) together.
If you want to get scientific about it, dew point is the temperature at which the water vapor (which we measure as humidity) condenses at the same rate it’s evaporating. You feel stickiest when the dew point is very close to the temperature outside. That is because the water vapor can’t evaporate fast enough, so it just hangs around. That’s why on exceptionally humid days, you feel like you’re living in a swamp, except the swamp is you.
Fog is the ultimate manifestation of dew point - it occurs when humidity is near 100% and the dew point is within a few degrees of the temperature.
Easy, right? Water vapor is what makes you feel sticky when you go outside, it’s what makes your hair frizz, it’s what makes you question literally every choice that has led you here, to this moment, to be outside.