

The Capitol dome reflected in ice. (Ian Livingston)

Temperatures may struggle to surpass 15 degrees in Washington tomorrow. Readings that cold or colder — if they occur — have been unseen since Jan. 19, 1994 when the high was 8 degrees.

Though we won’t challenge a low like we saw that day when it hit -4 degrees, should D.C. dip to 8 degrees on Tuesday or Wednesday morning, it will be the first time since 2009.

Below 8 degrees? That would be the coldest since at least 1996 when it was 5 degrees.

Those lows are within reach. Though a brief hit, this is big time cold on the way.

Setting the stage

Over the past 30 years ending 2013, D.C.’s average coldest yearly high was 23.3 degrees with a median of 23 degrees. The average coldest low was 11.3 degrees with a median of 12 degrees.

Within that period there was considerable variance when it came to a year’s coldest high, extremes were 8 degrees in 1994 and 32 degrees in 2012. Yet given the tightly packed mean and median, it’s a good guide for typical coldest of the cold every year.



The coldest highs and lows by year since the first full year of observations at Reagan National (KDCA). The dashed lines are for the current, ending 2013, 30-year average. (Ian Livingston)

Related: Putting an Arctic cold blast in perspective (Jan. 2013)

As noted during the strongest Arctic outbreak last year, and indicated by average daytime temperatures bottoming out, January is prime time for both regular cold and severe cold. Roughly seven in ten years in the D.C. record have seen their coldest daytime high in January, and similar with lows.

If D.C. manages to reach a high of 18 degrees on Tuesday, it’s the coldest since 2009. Anything below that is colder than we’ve seen since at least 1996, when readings only reached 17 degrees on Feb. 6. Below that is the previously mentioned unreachable mark of 8 degrees for a high on Jan. 19, 1994.

Unusually cold days in D.C.

The occurrence of daytime temperatures reaching only the teens or lower into Washington is an unusual event. The last time it happened was Jan. 16, 2009 when the high was 18 degrees. It has only been done three times going back to and including the punishing cold of 1994.

While we can go a full year without, days featuring highs only reaching the 20s or lower are much more common. D.C. averages four such days per year.

Highs in the teens or lower happen way less often, with about 0.3 per year per current averages — once every three years, but as in recent decades, quite often with much larger gaps.



Breakdown of cold highs at D.C. since 1946. (Ian Livingston)

When talking highs of 15 degrees or lower, we’re hitting truly remarkable air in recent decades. Outside the 8 degree high in 1994, there have only been six other instances (of 15 or lower highs) since 1946, the first full year of records from National Airport.

Looking at lows, we see a similar distribution between lows in the teens by year compared to lows in the single digits. Teens are to be expected, single digits not necessarily.

Despite lately lacking, lows in the teens should come on a number of occasions per winter. D.C. averages between eight and nine lows this cold over the last 30 years. Lows in the single digits or colder average 0.7 times per year. In the 2000s, we’ve only seen it happen twice and none below zero since 1994.



Breakdown of cold lows at D.C. since 1946. (Ian Livingston)

Low temperature benchmarks are a little less clear cut given that it is seemingly harder and harder for D.C. to achieve the coldest of the cold lows. Nonetheless, around 8 degrees is where we’ve tended to settle on our chilliest nights of late (2009, 2004).

The last time D.C. fell below 8 degrees was Feb 6. 1995 when it was 7 degrees. Since 1994’s -4 degree reading, lows below 8 degrees have happened three times.

Yeah, but D.C. is a warm spot…

A better idea where a good portion of those folks north and west of I-95 and east of the foothills need to target temperature-wise for extreme cold might come from Dulles.

Zero degrees and below is historically most common at Dulles out of the big three local stations including Baltimore. Zero or below is a very real possibility there. The last occurrence of such happened on Jan. 17, 2009, when it hit exactly zero.

Below zero? Feb. 6, 1996. One of three that year. Interestingly enough, before 1996, Dulles saw at least one day below zero in two out of three years after it became an official climate location.



Days per year with lows below zero at Dulles, Va. since 1963. (Ian Livingston)

There has either been two decades without much super cold overall in the region, or the local climate around Dulles has been impacted enough by urbanization to make getting below zero more difficult than it used to be. Probably a mix of the two.

On the cold high end, should the temperature fail to reach past 15 degrees, it’ll be a first since January 1994 at that location as well. In the entire record at Dulles, winter (Dec.-Feb.) days with a high of 15 degrees or less made up 0.3 percent of all days.

Washington area cold records to watch for

Though powerful, this is a quick shot. Tuesday is the big cold day. D.C. has a legit chance at breaking records for January 7 that have held for 130 years.

Here’s a rundown of what each local airport needs to reach on both sides of the books:

For D.C. to set daily records we’re targeting two 1800s dates for Tuesday. To get a record low max, we need to tie or best 18 degrees set in 1878. To snag the record low, we’d need to tie or beat the 5 degree mark set in 1884.

At Dulles, the high needs to be 21 degrees or lower to tie or set a new record last reached in 1996. A low of 8 degrees or below will do it for a daily record low, now held by 1988.

Baltimore records in play are from the same years as Dulles. A 22 degree or lower high would tie or surpass a record last set in 1996. When it comes to a low, anything 8 degrees or below sets a record created in 1988.

Wednesday morning records are zero in 1878 at D.C. (very unlikely), -4 degrees in 1970 at Dulles (very unlikely), and 4 degrees in 1970 at Baltimore (40% chance?).