FRESNO, Calif. (KGPE) – Did you notice how muggy it was on Friday? This was thanks to the Four Corners ridge of high pressure steering the monsoon moisture our way.

The monsoon moisture has also been providing the Sierra with showers and storms all week long, even bringing flash flooding concerns to some areas. Even the Central Valley had a few Friday morning showers.

Ridge of high pressure near the Four Corners has been sending monsoon moisture our way

It was more humid than normal throughout the week, but we really felt it on Friday. How can we express how muggy it feels outside? Meteorologists typically use the dew point instead of relative humidity.

Relative humidity (RH) tells you how close the air is to saturation, relative to the temperature. In other words, it’s the amount of water vapor in the air compared to how much water vapor the air can hold at the current temperature. It’s not the best way to describe how humid it feels outside. It can feel comfortably dry with a high relative humidity value. You can also have lower relative humidity, but the air feels grossly muggy. You’ll read examples of this in a moment.

The dew point is the measure of water vapor in the air. If the air is cooled to the dew point, it’s now saturated (100% relative humidity). The higher the dew point, the more moisture is in the air, and the more sticky it will feel. If the dew point is lower, there is less moisture in the air, and we feel better (even with the 100% RH). This makes the dew point more relatable to our lives.

For example, it can be 40° outside with a dew point of 40°. The relative humidity is 100%, but the dew point is low. It doesn’t feel muggy.

Or, using today’s numbers during the 5 PM news: the temperature was 90°, the dew point was 67°, and the relative humidity was 47%. Even with the lower RH, it sure felt humid! Check out the 5 PM data below.

Here’s a scale to help you gauge how it feels based on the dew point, with the arrow pointing to today’s range for most of the day.

The next time you’re wondering if it’s muggy outside, try looking at the dew point instead of the humidity. For reference, we spend many days with dew points in the 40s and low 50s in the Central Valley, even in the summer.