January 2014: the coldest in decades in D.C. by many counts

2014 or 1977? (Erin Kelly via Flickr)

Jan. 27, 2014 or 1977? (Erin Kelly via Flickr)

Although the final average might not quite portray the true sense of this January’s cold, the D.C. area has seen some remarkably frigid temperatures this month. The coldest in decades on many counts.

Much of the “average issue” is due to considerable variability. Even if we never got super warm and spent much more time shivering, any mild air in the heart of the coldest time of year can quickly mess with the final number.

And so it’s not clear whether to characterize the month as simply formidably cold or a truly historic one. It probably ends up somewhere in the middle, as we’ll examine below.

Top-10 coldest days since/including 1994

2-top10-coldest-2decades-ending20141994 is a good reference point when it comes to severe cold, given it’s the last time D.C. got below zero. 1994 also produced the second coldest (tie) high temperature — 8 degrees — in the whole modern recorded history of the city going back to the 1870s.

Since 1994, a strong case can be made that regular instances of significant cold have been far less frequent than prior decades.  This month has turned that tide a bit, as we’ve managed two of the top 10 coldest days in that 20-year span.

Both of these big-time cold days over the past few weeks featured lows in the single digits for the city, the most single digit or lower readings in any month since Feb. 1996 (2) and any January since 1994 (6).

Cold lows: We can still do them!

High temperatures have not been as notable as the lows. While it was newsworthy to have a day with highs holding in the teens last week (and we’ve arguably been “robbed” a day or two more of highs that level or colder thanks to midnight highs), the 19 degrees on January 22 was still warmer than 18 seen on January 16, 2009.

January 2009 is also likely to finish colder on the whole than this month — more on that later…

On the flip side, the lows this month have been seriously and consistently cold. Nearly half of the month has featured low temperatures we sometimes only see once or twice in a mild winter.

Number of lows in the teens or less by year in January at Washington, D.C. (Ian Livingston)

Number of lows in the teens or less by year in January at Washington, D.C. Blue in 2014 are “potential days.” (Ian Livingston)

Let’s consider lows in the teens or lower this month. D.C. might expect 4.5 per January looking at the average for last 30 years ending 2013. Through today, Washington has seen 11 lows in that category.

We have a realistic chance to add one or two more days in this grouping, which would be the most since 2004 when we saw 12, or 1988 when 14 occurred. If we reach twelve days or more, we’re in the realm of about 15 percent of all Januaries since 1871, and that number or more has only happened eight times at Reagan National Airport.  Most occurred the previous record station downtown (prior to 1945, at 24th and M St.).

At Dulles, where temperatures are usually among the lowest in the metro area, the current 30-year average of 2.4 days with lows in the single digits or lower has been blown out of the water this year, with 9 so far. One must go back to January 1994 to find a month with 9 mornings that cold. If Dulles makes it to 10 days, it’s the most in a month since 1988 when that number was reached. The most on record there for a month is 13 in 1977. Rare air.

January average, cold but not truly historic

No doubt it’s been cold, but it isn’t the winter equivalent of a July 2011. On a monthly temperature average basis D.C. is poised to easily crack the top 20 Januaries since records have been kept at National Airport (1946 was the first Jan.). It’s going to shoot for roughly top 40-45 overall, going back to the 1870s.

The coldest Januaries by average temperature in D.C. since observations have been taken at DCA. For comparison, 1977 is number five all time back to the 1870s. (Author adaptation of NWS LWX data)

The coldest Januaries by average temperature in D.C. since observations have been taken at DCA. For comparison, 1977 is number five all time back to the 1870s. (Author adaptation of NWS LWX data)

Even though 2014 may fall short of three other Januaries in the 2000s (2009, 2003 and 2004 in order of coldness) per overall average, the month produced briefer periods of extreme cold that outdid anything seen in any of those years.  It was just not quite wall-to-wall cold.

In the middle of the month, we had a week of temperatures at times well above average, including a high of 61 on the 13th, that helped keep us fairly close to normal before the lengthier set of polar punches of late. But even within that we saw a day like yesterday, frightful on the way home, it was offset by a high of 54, making it a little warmer than average for the date.

Maybe average really isn’t a tell-all metric anyway, especially in a volatile temperature month? In this one, I’d argue it’s not.

Also on Capital Weather Gang

D.C. area forecast: Bitter cold today, slight snow chance tonight