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Published on Jan 16, 2015
Why isn't the first day of Winter the coldest?
I'm Storm Shield Meteorologist Jason Meyers, and since we get all of our heat from the sun and the first day of Winter has the least amount of daylight, it should be the coldest day of the year, right?
Wrong. And it's because of a phenomenon called seasonal lag.
Winter begins with the winter Solstice - and for all of you in the northern hemisphere, it happens on December 20, 21, 22, or 23. In the southern hemisphere, just flip those dates to June. All of it has to do with astronomy, not meteorology.
The Winter Solstice is the shortest day of the year. We have the least amount of daylight all year long because the earth is tilted away from the sun on this day more than any other day of the year.
The amount of heat gained from the sun is at a minimum on the first day of Winter, but since different parts of the earth - rocks, soil, and water - absorb and release heat at different rates, it takes anywhere between a couple weeks and a month for the coldest weather to catch up, which is why for most of the northern hemisphere, January is the coldest month of the year.
On other planets, seasonal lag isn't as prominent. Mars, for example, is made up of very similar elements that absorb and release heat at the same, fast rate, so it's coldest day of the year only a few days after the first day of Winter.
So stay warm, and thanks for watching. Just don't lag in hitting the like button.