A balmy 60-degree day in early January might feel like spring, but when darkness falls around 5 p.m., we’re inevitably reminded that it is still winter. Now, at least, we’ve got the longer daylight and higher sun angle to accompany our spring-like temperatures, even if they are (once again) several degrees above average.
Unless you’re trapped in a windowless building at 6 p.m., you’ve probably noticed that the evening sky is a lot brighter than it was at the same time a month or two ago. The D.C. metro area has gained 1 hour and 41 minutes of daylight since the winter solstice on Dec. 22. The sun now sets at 5:55 p.m., a full 1 hour and 9 minutes later than it did in early December. Tack on a half hour of twilight and we now have some daylight stretching into the dinner hour.
Early risers are starting to see more morning light as well. Sunrise was at 6:48 a.m. today, which is 36 minutes earlier compared with the winter solstice. The uneven shift in sunrise and sunset times as the days lengthen is caused by the later shift in solar noon, the time of day when the sun reaches its highest point in the sky.
Increasing day length is just one factor responsible for the gradual rise in average temperatures as winter transitions to spring. Also important is the sun’s higher path in the sky, which heats the ground and air more effectively. At solar noon, the sun in D.C. now climbs to 41.6º above the horizon (certainly higher and brighter than its 27.7º declination on the winter solstice).
Snow lovers and winter enthusiasts like myself have undoubtedly been disappointed by the lack of snow this year. Unfortunately, the longer days are but another reminder that the “non-winter” of 2011-2012 will unlikely be resurrected before spring begins in earnest.