Weather Blog

By Steve MacLaughlin

I have this love affair with the dew point. I’ve written about it before. I tell my friends about it. I talk about it during my newscasts quite frequently. The fact is, it is the most important number in all of weather, even though most people don’t quite know what it means. But it is everything, and today is a great day to talk about part of its grasp on our lives.

I won’t get into all the science of dew point; it is complicated. The basic definition is the temperature at which condensation occurs. In other words, the temperature to which the air temperature has to fall for all of that moisture floating around in the air that you can feel but can’t see (gas) to turn into moisture we can see (liquid) as clouds or fog or dew or rain or even solid snow or ice. When the air temperature drops to the dew point, the relative humidity is one hundred percent, the air is saturated and condensation and usually precipitation occurs.

The much easier principle to understand needs very few words. If you were outside on Saturday and outside again on Sunday, then you know what the dew point is.

On Saturday, the dew point was 73 degrees before the storms rolled thru. That is incredibly humid. About as bad as it gets around here. If you were outside, you got hit with what felt like a wall of water and the heat index soared to the triple digits with all the humidity.

On Sunday, behind a cold front, northwesterly winds not only cooled us off, but dropped the dew point to 33 degrees. That is incredibly dry. As dry as some winter days. If you stepped outside it felt like a different part of the country. It simply felt wonderful. That is the low dew point and the very dry air.

If you work outside or like me, run outside, you look for low dew points because when it’s drier, it not only feels better, but our bodies are more efficient at keeping cool. Today’s level of moisture is a gift; a rare commodity as we enter the late spring and summer.  Most summer days feel more like Saturday than Sunday.  With high dewpoints in the 60s and 70s, the air temperature feels even hotter. That is the heat index; the temperature our bodies think it is because humidity (high dew points) makes it harder to stay cool.

Enjoy, Happy Mothers Day and have a great week,

Steve Mac