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January is the subject of many weather maxims. As we bundle up for these sometimes dreary days, it’s fun to consider how much of this month’s timeless wisdom will hold true.
The first 3 days of January rule the coming 3 months.
While the day-to-day weather can change very quickly as individual weather systems move across the country, the overall weather pattern tends to stay the same for 90 to 120 days, anchored by teleconnections such as El Niño and the North Atlantic Oscillation, which remain relatively stable. Thus, in most cases, however much the weather has departed from normal in recent days is likely to be the overall direction of departure in the coming months.
If birds begin to whistle in January, frosts to come.
Birds are usually around and active in the northern states during the heart of winter only when temperatures are unusually mild, which means that the steering winds high aloft have a large north–south component. The southerly component is what brought the warm weather, but, as those steering winds move, they will become northerly, bringing along very cold air.
Always expect a thaw in January.
The “January thaw” is a name given to a mild spell in January in places where temperatures are below freezing most days. While it does not occur every year, given the normal variations in temperature and weather patterns, most Januaries have at least a few days when this happens.
As the day lengthens, the cold strengthens.
As you may know, the winter solstice occurred on December 21 in the Northern Hemisphere. This is the day when the Sun is farthest south and the duration of daylight is least. With the Sun at its weakest, you might expect that this would be the coldest day, on average—but it is not! Think about what happens when you put a tray of water in the freezer. It does not become ice instantly, because it first has to give off its stored heat. The same thing happens with Earth, so the coldest period occurs, on average, about a month after the winter solstice, even though there is more sunlight then. Hence the coldest temperatures typically occur as days are getting longer.