John Wheeler, WDAY, Published September 15 2012
Weather Talk: Dry air one of the reasons weather has been erraticIn most autumn seasons recently, there has been a tendency for the first freezing temperatures to arrive about a week later (on average) than has traditionally been the case.
There can be several reasons for this. There has been a slight overall warming of our climate with a significant portion of that measured warming occurring at night.
But some of the reason may be the 19 years of mostly wet weather. This fall, the air has been extremely dry, and we have already had several brushes with near-freezing temperatures. Water vapor gives air a higher specific heat capacity, and so it changes temperature less readily than dry air. But when air is very dry, there is a tendency for warmer days as well as cooler nights. This explains why the weather this fall has been so erratic, ranging from the 30s to the 90s in just the past few days.
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