After the Solstice
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Hi I'm Dave Thurlow for the Weather Notebook. Listener Alaina Bailey from Concord, New Hampshire, who hears us on WEVO, sent us the following: Why is it that the shortest day of the year occurs at the beginning of winter? It seems to me that if the coldness is caused by the low angle at which the sun hits the earth, that the first day of winter should be the coldest. So, why is it coldest in the middle of winter?

That's a good question and the same is often asked about the summer, only about heat, not cold. And seeing that it's now summer, let's look at things from this point in the season. The longest day of the year was June 20th. That means the sun on that day was as high as it gets in the sky, it's rays most concentrated and longest lasting. Starting the next day however, the sun began to lower and the days began to shorten. Yet, in spite of this, the heat of summer is still on the rise.

The inverse happens after December 21st each winter. As the days lengthen, the cold strengthens, an astute observer once noted.

Look at it this way. The earth is a kitchen sink. As long as the water spouts from the faucet quicker than it runs down the drain, the sink will fill. On June 20th the faucet's on full blast. It starts to slow down gradually but for a while there is still more coming in than going out. It isn't until about mid August that the outflow is more than the inflow. The sink drains, the earth cools. Now take the same thing and sorta flip it around and you have winter when as the days lengthen the cold strengthens. Check weathernotebook.org for more.