The humidity of the air affects your comfort and the stress that the weather puts on your body. So the National Weather Service reports a quantity called the heat index, or "apparent temperature" to try to give you a sense of what the air temperature feels like if the effect of humidity is taken into account.

As an example, a temperature of 95^oF and a relative humidity of 50% produce a heat index of about 105^oF. That's high enough to make heat stroke possible.

But other factors also affect how you feel, such as the color, fabric, and thickness of your clothes, and whether the wind is blowing. The heat index doesn't take any of these into account. But you'll certainly feel more comfortable on a hot humid day if you're wearing thin and loose-fitting clothes and there's a breeze.