With these dangerous heat indexes being recorded almost daily this week, you may have noticed it's a bit harder to cool off outside. That's because your body's cooling process, sweating, is not able to perform as well as it should.
This is because of how humid it has been this week. We've been tracking dewpoints in the high 70s and low 80s over the past couple of days, and temperatures in the high 90s. With these to values combined, we have been seeing the heat index get up into the 105-115 range daily.
With how hot it's felt, your body's first instinct is to cool itself off by sweating, but the cooling process isn't nearly as effective with the current humidity. Typically, with low humidity situations, your body sweats, and the sweat evaporates. Since there isn't much water vapor content in the atmosphere, the sweat can evaporate with ease. Evaporation is actually a cooling process, which is why that sweat evaporating from your body helps you cool down.
With high humidity settings, like today, the water vapor content in the atmosphere is so full, so there isn't nearly as much space for the sweat to evaporate. So, instead of the sweat evaporating and cooling the body down, it stays on your skin, making it feel much more uncomfortable. On top of this, your body still wants to cool itself off, which is why you continue to sweat. This can lead to loss of fluids in the body and dehydration.