Monthly precipitation in January is about as low as it gets during the year, thanks in large part to the cold temperatures not being able to hold much moisture. And for snow lovers, January cannot be beat. Normally, it tops all months with the highest snowfall average. Rarely does a January go by without at least a ground coating or two.
Keep reading for more in this tenth installment of a year-long series of posts detailing specific statistics on climate norms, extremes, and averages for the each month in Washington, D.C…
The 1981-2010 average* monthly precipitation for January is 2.81”. That’s a decrease of 0.40” from the previous (1971-2000) average, and that departure is the most significant of any winter month as well as one of the larger of the year. This is somewhat unusual for a cold-weather month, with December totally stable from the prior average and February only losing 0.01”.
The most rain Washington has seen on one day in January is the 2.77” on the 12th in 1915. Only four days in the month have witnessed 2” or more of rain, the lowest of any month in the year. All of these instances also had relatively mild daytime temperatures except for the 28th in 1922 -- the great Knickerbocker snowstorm.
When it comes to the wettest month, 1937 is tops with a total of 7.83” -- one of only six Januarys with a precipitation total past 6” of liquid (rain and snow mixed). The driest month on record is 1955, when only 0.31” of precipitation fell on the city.
Normal snow for the month of 5.6” is the seasonal peak locally, but it’s also 0.6” less than the previous climate normal. Of the five months with snow (Nov-Mar), this was the largest change, due to reduced overall precipitation in recent decades during the month.
Roughly 300 events with accumulation of 0.1” or more (including systems that were largely rain) have occurred in January throughout history. This comes out to over 30% of the all D.C. snow events and as might be expected, the most of any month. Close to 40% of all D.C. snow events of 5” or more snow occur in January, though it is basically tied with February on this metric (both considerably snowier than all other months in D.C.)
The biggest snowstorm of January (and all-time) is the aforementioned Knickerbocker snowstorm that dropped 28.0” in Jan 1922. It is well known for its hefty amount of wet snow. Almost two and a half feet of the waterlogged stuff caused the Knickerbocker theater roof to collapse, killing 98. More recently, the Blizzard of 1996 (Jan 6-8) brought between a foot and a half and three feet of snow to the region.
Not surprisingly, the Knickerbocker snowstorm also set the record for the most snow to fall in one day at D.C. when 21” fell on the 28th in 1922. Second place is 16.4” on February11, 1983; 3rd is the 15.0” which fell on December 19, 2009. The 26” of snow on the ground during the Knickerbocker storm (on the 28th) ranks just behind several daily snow depths during the 1899 blizzard aftermath in the snowiest February (and month) on record.
If you’re not a fan of chilly weather, January might be your least favorite month of the year for good reason. Washington is no Fargo, ND by any stretch of the imagination but January is still quite cold on average. The normal monthly temperature of 36.0 degrees, a marked increase from the previous 34.9 degrees. That 1.1 degree increase is the largest of not only the winter months, but also of the entire calendar year. Bad news if you love wearing that heavy coat?
The warmest January on record is 1950 when the average was 48 degrees. To put that in perspective, it’s about 2 degrees cooler than an average November and 1 degree warmer than an average March. Toasty, right? The coldest January on record was the frigid 1918 that came in at 23.7 degrees. It’s been as cold as 25.4 degrees at Reagan National Airport (1977) where temperatures have been recorded since the early 1940s.
Daily high and low temperatures bottom out in mid-January, exhibiting a slight climb from start to finish after the dip. Normal high temperatures rounded to the nearest degree of 43 degrees run from January 2 to 22. The absolute coldest average high of 43.1 degrees spans from January 6 to 16. Lows reach their rounded coldest level of 28 degrees from January 12 to 23 and are absolute coldest from January 15 to 20 at 28.3 degrees.
Using the current climate period of 1981-2010 as a guide to the expected, we can plan on about 36% of January highs to reach the 40s and 27% to top out in the 30s. 19% make it to the 50s with 8% each in the 20s and 60s. Temperatures in the 70s, the 10s and single digits make up the remainder. Lows in the 30s barely outpaced those in the 20s at 39% and 35% respectively. Lows in the teens are more likely than lows in the 40s, at 14% and 9% each. Single digits, 50s and negative numbers make up the small percentage left.
Like December, no January day has hit 80 degrees or higher. But, it just missed in 1950 when the thermometer reached 79 degrees on the 26th. As recently as 2002, D.C. hit 77 on the 30th, which ties for the second warmest of the month along with the 15th in 1932. Way on the other end of the scale, the coldest high of 8 degrees happened both on the 13th in 1912 and the 19th in 1994. That’s cold!
While December has no lows of 60 degrees, January has had two, its warmest days of the month. The first instance was the 13th in 1932 and the second was the 4th in 1950. There have been 19 instances of lows below zero in January, and the coldest of them was -14 degrees on the 1st in 1881, the second coldest reading ever in Washington. The coldest National has been in January is -4 degrees on the 19th in 1994.
30-year (1981-2010) Averages / Overall (all history) Averages...
Highs below 50: 22.4 / 23.1
Highs below 40: 11.2 / 12.4
Highs 32 or less: 4.8 / 5.2
Highs 60 or above: 2.7 / 2.5
Lows below 40: 27.8 / 28.3
Lows 32 or less: 20.3 / 21.6
Days with at least a trace of rain: 14.2 / 15.0
Days with .1” of rain or more: 5.6 / 6.6
Days with .5” of rain or more: 2.1 / 2.1
Days with 1” of rain or more: 0.6 / 0.6
Days with at least a trace of snow: 7.0 / 6.7
Days with 1” of snow or more: 1.6 / 1.7
Days with thunder: 0.3 / NA
Days with hail: 0.0 / NA
-This count is done through records on Weather Underground, and does not include the entire historical period.
All-Time Records (High / Low)...
Highs below 50: 31 (1881, 1977) / 10 (1913, 1950, 1990)
Highs below 40: 28 (1918, 1940) / 1 (1932)
Highs 32 or less: 19 (1918, 1940) / 0 (15 years)
Highs 60 or above: 14 (1950) / 0 (37 years)
Lows below 40: 31 (35 years) / 14 (1932)
Lows 32 or less: 31 (1918, 1977) / 4 (1932)
Days with at least a trace of rain: 22 (1907, 1937) / 7 (1967)
Days with .1” of rain or more: 13 (1937) / 1 (1872, 1955)
Days with .5” of rain or more: 7 (1882, 1892, 1937) / 0 (13 years)
Days with 1” of rain or more: 2 (1891, 1978) / 0 (79 years)
Days with at least a trace of snow: 15 (1982) / 1 (1889, 1973, 1974)
Days with 1” of snow or more: 7 (1905, 1925) / 0 (27 years)
Days with thunder: 3 (2006) / 0 (23 years)
-Same as above. (30-year high / low listed)
Daily climate records for Washington, D.C., 1871-present
- See selected and additional statistics compiled for this post (Excel)
*All averages or normals, unless otherwise noted, refer to the 30-year period of 1981-2010. Unlike initial months, a full set of new climate norms is now available and will be used throughout. Past months will be edited to reflect the new norms.
While numerous local climatology statistics including daily, monthly, and seasonal normals and records are available from National Weather Service Baltimore/Washington, there are myriad other pieces of information which help frame the story. Rather than attempt to recreate what is already available, this series of posts will act as a companion to most information presented there.
This is the tenth installment of a series of living documents. Through early 2012, each month will be broken down in a similar or evolving way. As input is taken from the community, some items may be added to or changed in older postings. These postings will be updated as necessary to reflect changes when needed. Other articles may also become part of this series.
Feel free to share thoughts or additional data you may be interested in seeing.
Learn more about each month:
-April weather in Washington, D.C.
-May weather in Washington, D.C.
-June weather in Washington, D.C.
-July weather in Washington, D.C.
-August weather in Washington, D.C.
-September weather in Washington, D.C.
-October weather in Washington, D.C.
-November weather in Washington, D.C.
-December weather in Washington, D.C.
-January weather in Washington, D.C. (viewing)
Article last updated: January 12, 2012.