Ian Mackey

Why dew point is the true measure of comfort

I learned something new when my fiancée explained why I should care about the dew point.

She recently started running early morning to avoid the desert heat. We live in the desert, where it's hot—averaging 101°F. Last summer, it was so hot that even the cacti died.

Despite the cooler mornings in the high 70s°F or low 80s°F, she'd return drenched in sweat, wondering why running felt so hard. Running in the morning should be easier, right? The temperature tends to increase throughout the day.

Temperature affects your daily comfort and activities, but the dew point is essential for understanding your comfort level.

People say, "I can't stand Florida; it's so wet and humid. I'd rather live in a dry climate like Arizona." This is where the dew point comes in.

The dew point is the temperature at which air becomes fully saturated with moisture. A high dew point means more moisture in the air, making it harder for sweat to evaporate from your skin, leading to discomfort.

At first glance, 100% relative humidity seems unbearable. But that number alone doesn't tell the whole story. On a 40°F day with a dew point of 40°F, the relative humidity is 100%. Compare that to a 90°F day with a dew point of 70°F—typical Florida weather. The relative humidity is about 52%, yet it feels more humid and uncomfortable due to the higher dew point.

The dew point doesn't fluctuate much throughout the day. Today, it peaked at 53°F and will drop to 48°F tonight.

Here's a guide to comfort levels based on dew point:

Next time you check the weather, don't just focus on the temperature. Check the dew point—it's a more reliable indicator of your comfort outside.