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The cold snap the D.C. area just went through was one for the ages

Cold weather gear. (Kevin Wolf <a href="">via Flickr</a> )

The stretch of winter cold we just went through was about as intense as it comes. If you can’t recall such a long and strong cold shot, it’s for good reason — there aren’t many in recent history.

It arrived early in the winter, settling in around Christmas, and turning it up a notch in the days before the New Year. We then dealt with intense to extreme cold through the past weekend.

Among the most astounding numbers:

  • 1918 – the last time we saw a colder final week and first week of a year in D.C.
  • 12 – the number of consecutive days it was at or below freezing at Dulles, a new record.
  • 19 – the average temperature of the first week of January, the fourth-coldest on record for D.C.

And that’s just a few.

One quick way to visualize how it looks compared to normal and compared to our recent weather is to look at a long-term temperature departure timeline. A glance shows that this latest stretch (on the far right) was much, much colder than normal.

Other takeaways are the intensities of the departures. In what is largely a sea of red, there are now a number of days in a row of extreme cold. National Airport alone recorded daily temperature departures of minus-19 on Jan. 5, minus-20 on Jan. 6, and minus-20.4 on Jan. 7.

As you might notice above, we do that kind of departure on the warm side fairly frequently. On the cold side? Rarely.

For the D.C. region, the story of this cross-year Arctic onslaught is focused on longevity, but the depths of the cold were also impressive.

Consider again that the two-week stretch from Christmas through Jan. 7 was the fifth-coldest two-week year-change overlap on record in D.C. It’s the second-coldest on record for Baltimore, and the coldest at Dulles. It was a similar story all around us.

While compiling notable numbers for this post, I came to the conclusion that there may be too many to count. Below are some of the most eye-popping locally, and I am sure I have missed plenty.

Daily records 

As CWG’s Justin Grieser pointed out a few years ago, D.C. warm records are vastly outpacing cold records . Getting any cold records often seems like a huge deal. We pulled a number out of the hat this stretch:

  • Dulles (where records begin in 1963) set record-low maximum temperatures on Dec. 28 with 23, Jan. 1 at 23, Jan. 5 when it reached 19, and Jan. 6 with a high of 19. Baltimore (where records date to 1872) tied a low max for Dec. 28 at 24. D.C. (since 1872) tied its coldest max at National Airport (since the mid-1940s) for that same date of 25.
  • Baltimore recorded a record low of 10 on Dec. 28, and it reached 1 on Jan. 7, which also set a record low for that date. Dulles reached record-low temperatures on Jan. 3 with 1, and Jan. 7 at minus-1.
  • D.C. didn’t set any record lows, but the low of 8 on Jan. 7 was the coldest since 5 on Feb. 20, 2015. Prior to 2014 and 2015, National had not reached the single digits since 2009.

Lengthy cold streaks

In addition to the aforementioned coldest final week plus first week of a year since 1918, here are some other key local tidbits about the longevity of this cold wave:

  • D.C.’s run of 12 days at or below 35 degrees is the sixth-longest on record. It’s also the longest at-or-below freezing streak since February 1961. Further, the consecutive lows at or below 16 is the fifth-longest streak on record at eight days.
  • Dulles set a record for the longest stretch at or below freezing, with 12 days. The below-freezing weather stretched well into the 13th day before rising above freezing in the evening. This record beats prior ones by more than two days.
  • Baltimore’s 12 days in a row of 33 or lower ties for the third-longest streak in its long-term record. Only two are longer: 14 days ending Feb. 18, 1979, and 15 finishing Feb. 2, 1966.

More trivia to impress your friends

  • The high of 23 on Dec. 31 in D.C. was the coldest high temperature in the month for the city since Dec. 24, 1989, when it was also 23.
  • Four days with lows in the teens are the most in December since seven in 2000. The 12 days with lows in the teens or lower for the final 10 days of December and first 10 days of February are the fourth-most on record for that period, and this is the first time it has happened since January 1918.
  • Jan. 5-7 was the first time with consecutive days of 21 degrees or less for highs in D.C. since Feb. 3-5, 1996, when there were three such days in a row. Interestingly enough, that was also a La Niña winter.
  • Canaan Valley, just 125 miles west of D.C., reached minus-24 on Jan. 7. The average low temperature for the first week of January was minus-10 there. (h/t former NWS climatologist Robert Leffler.)

Now we mild up, at least briefly. Even in the coldest winters there is often a “January thaw.” It might not always come in January, but it is hard to sustain punishing winter weather for an entire winter. As weather watchers know, it rarely stays the same for long.

The pattern that helped bring us this big blast of cold is one that tends to repeat itself. I’m no long-range forecaster, but I’d wager it’s a wise idea to enjoy the warmth we get and brace for more winter before it eventually gives way to spring.

The data detailed in this post comes from xmACIS2, NWS Baltimore/Washington, and long-term research by the author.