Blog: It’s not the heat, it’s the humidity

Humidity on a hot summer afternoon – it’s the air you can wear many say, the air that feels so thick and heavy it’s like we’re nearly swimming instead of walking. Why?

Short answer, the air is saturated.

The dew point is the decider to us humans, it’s the value that truly depicts how the air feels. The higher the dew point, the higher the humidity. The lower the dew point, the lower the humidity.

Essentially, it’s the air’s saturation point. When dew points reach the 60s & 70s and start to inch closer to the air temperature, the air gets closer and closer to saturation. The air fills with water as millions and millions of water vapor molecules attach themselves to the air particles. So to us humans, it feels muggy, thick & heavy.

Temperatures compared to dew points this afternoon.

But in fact, humid air is actually lighter than dry air. So that walk-off homerun UVA crushed in the bottom of the 10th the other day probably traveled a bit farther in the humid South Carolina air. The molecular weight of water (H20) is lighter than that which makes up dry air (Nitrogen & Oxygen). So why does it feel so muggy, thick & heavy?

Because our perspiration can’t evaporate.

In the hot summer sun, our bodies begin to perspire and release heat. To cool off, we need that heat to escape off our skin. However, during those muggy & humid days, that heat being released from our bodies can’t escape, and our sweat can’t evaporate, because the air is already full of so much water.

It’s the equivalent of trying to dry yourself off with a wet towel.

So yeah, most of the time in our neck of the woods, it’s not the heat, it’s the humidity.

It’s also that same humidity which makes the air more capable of producing rain, since it’s already full of so much water. That’s precisely the case we have for the next few days – Wednesday and Thursday will feature the humidity and late day showers and thunderstorms.

We’ll watch for scattered showers, downpours and thunderstorms this evening.

Towards the weekend, we should get a shift in the wind out of the north, which will brief bring in some drier air to help break the humidity and drop temperatures a bit.