WEDNESDAY, MAY 17 - RELATIVE HUMIDITY: AN IMPOSTER?


As summer approaches, we all want to know "will today be humid?". So we certainly need a reliable measure of how comfortable the air feels. But the familiar "relative humidity" isn't the answer.

To see why not, here's an example. Imagine a humid July morning - 70oF, 90% relative humidity. No surprise, you say - it's humid, the relative humidity should be high. Let's say that later that day, the temperature hits 95oF, and it's still very muggy. But now the relative humidity will likely be about 50% - that's right, 50% - which can be very misleading to sweaty weather consumers.

The problem is that relative humidity depends not only on how moist the air is, but also on the temperature. As air heats up, the relative humidity goes down, and vice versa. That makes relative humidity an imposter as a gauge of how humid the air feels. Tomorrow night, I'll introduce you to the real deal.

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