Tuesday, January 21, 2014

Tomorrow Is Washington's "Winter Temperature Solstice"

With another "polar vortex" working it's way into our region, we're sure some of you are wondering when it's going to warm up again.

Well, have no fear, the winter temperature solstice is upon us as of tomorrow.

What do we mean by "winter temperature solstice"?  Well, that's the point in the winter when the average temperature reaches its lowest point--kind of like the shortest day of the year.  So, tomorrow (Jan. 22) the average high temperature in DC is 43 degrees, and the average low is 28 degrees.  (Forget about the fact that the forecast high tomorrow is 18 degrees--we're talking averages here!)  The next day, Jan. 23, the average high will jump up to 44 degrees, and the day after the average low will go up to 29 degrees.  So, on average, from here on out--until mid-July--the average temperature will be rising.  Hooray.

Of course, our winter temperature solstice is not as reliable as the real winter solstice, which is absolute.  It may very well be colder--or warmer, but not this year--than average on Jan. 22.  But you get the picture--we've turned the corner, in terms of temperature averages.

It's interesting that, as a general rule, in Washington, DC (we're not sure if this holds up in other locales), the temperature runs about 30 days behind daylight.  In other words, it takes about 30 days after the shortest day for us to get to the lowest temperature, and it takes about 30 days after the longest day for us to get to the highest temperature.

This is why Fall in Washington is usually much nicer than Spring--in Spring, as the days get longer, the temperature is lagging a month behind.  Conversely, in Fall, as the days get increasingly shorter, mild temperatures continue to prevail.

Don't believe us?  The vernal equinox (the day on which the amount of daylight equals the amount of nighttime) is March 20 this year.  On that date, the average high temperature is 57 degrees.  The autumnal equinox will occur on September 23, when the average high is a much balmier 77 degrees.  It's not until late November that the average high gets back down to 57!

There you have it--it certainly is not going to feel any warmer over the next few days.  In fact, it is likely to be the coldest spell of the season, accompanied by lingering snow from today's storm.  But ever so gradually, the atmosphere is warming up, with temperatures starting to rise.  Before long it will be Groundhog Day, and we'll really know when Spring is going to start!

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