Several Miscellaneous Weather Notes Today:

Cold Air = Low Humidity

The cold weather in Atlanta on January 17th and 18th didn’t break the record low we saw back on December 20th, but only by 2.3 degrees. We recorded a low of 19.2 this morning at my weather station, the December record was 16.9 degrees. The low tonight is only expected to bottom out at 21, and then Wednesday and later in the week should see warmer temperatures.

One of the impacts of the cold weather has been an extremely low dewpoint - recorded at -2.3 degrees this afternoon. This is the lowest dewpoint I could find recorded by my weather station in the last three years, except for a slightly lower reading following the December cold snap last year.

Because relative humidity and dewpoint are related, we saw an outside RH of 18% — Extremely low. Unless you have a humidifier in your house, you may have had even lower humidity inside. Relative humidity measures the amount of water vapor in the air, compared to the amount of water vapor the air could hold before the vapor would condense into water droplets. Because warmer air can hold more water vapor than colder air, the cold air that seeps into your house becomes even dryer than it was outside.

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