Heat and humidity returns

For the past week or so, temperatures have been staying at or below the 90s with heat indices following closely behind. With all of the rain that has been coming through Mid-Missouri, one would think that conditions would be all around more miserable as far as humidity being higher than normal. But that is not the case. The rain is what has been keeping temperatures on the slightly less oppressive side. And with upper level ridging rearing up to persist for the rest of the week, the rain chance dwindles to 0% by Thursday.

When it does rain or right before or after, conditions are muggy, but this state of high humidity does not last. Due to water’s high capacity for “holding” heat, the runoff from the rain (or the water vapors that still remain suspended in the air) absorbs that heat in the air. So beginning Thursday when there is no chance of rain for the rest of the week and weekend, the air will have less water vapor. Water will evaporate from the ground and roads, leaving the ground dry and the air drier than they have been, as well. With less water to hold the heat, temperatures will rise.

But then how does the heat index get so high if it takes both humidity and temperature to make conditions oppressive? Although the air will have less water vapor in it, the water vapors that remain will have more heat to hold and will be near capacity. This results in the temperatures not only being high, but the air getting hot as well since there are less water vapors and in the air to hold the heat.