After a mild December and chilly, but tranquil January, February 2015 was almost like an entire winter wrapped up into just one month.
The average temperature of 30.3F at Washington, D.C. Reagan National Airport was the coldest monthly average temperature of any month of the 2000s (including all Januarys). You have to go all the way back to January 1994 (just over twenty years ago) to find a colder month, when the average temperature was 28.8F.
February 2015 saw seven days completely below freezing at National, which is the most since 1979’s 11 days. In terms of February-only periods, 2015 ranks as second coldest since 1950 (after 1979’s 28.4F), tenth coldest since 1900, and 14th coldest of all time.
The chart below plots all February outcomes for Washington, D.C. (as measured at Reagan National Airport, and at 24th and M St. prior to the mid-1940s):
We had an impressive ten days with temperatures 15 or more degrees colder than normal (that is more than one-third of the month!). You can see the remarkable daily details here including our five warmer-than-normal occurrences.
Reagan National recorded four highs of 22F or lower tying February 1979 for the third most that cold on record in February. All four of those days came in the second half of the month, which is the most in the long-term record for that period through the end of winter.
For Dulles Airport, the average temperature of 25.4F was the coldest February since 1979 and second coldest on record there. At Baltimore’s BWI Airport, its 25.3F average marked the coldest February since way back in 1934 (24.3F). In other words, we are talking several decades since we have seen a February this cold in the Mid-Atlantic.
Precipitation ran below normal, but snow was above normal. You can see how all three airports stacked up here compared to their respective thirty-year normal climatology:
After a slow start, snow outperformed climatology for February at all three airports. At Reagan National, the 1.68 inches of total precipitation was the 30th driest of all time and fifth driest of the 2000s. But, at the same time, it ranked as the fourth snowiest of the 2000s, just a tick behind last year’s 11.2 inches. You can see the rankings of February snow outcomes below:
Reagan National didn’t have any super-big snowfalls. It logged eleven days with at least a trace of snow and seven days with measurable snow concentrated in the second half of the month. Both Dulles and BWI picked up more than a foot of snow through the month.
Last winter experienced a cold and snowy February too. Here is how 2015 compares against 2014 at National Airport. We actually had more days of flakes flying this year versus last, but the snow events were beefier last February thanks to an overall wetter month:
With two cold February outcomes in a row, it is interesting to see the slight trend toward colder February periods in the 2000s at Reagan National. However, the warmest February of this century was only just three years ago in 2012, too. In fact, if you look closer you can see an upward trend from 2003 to 2012 and then more recently a downward trend again. It’s noisy!
Lots of Records Broken
Prior to this month, Reagan National had zero record low temperatures in February in the 2000s (the last record low it set in winter was back in 1994). The record low of 5 back on February 20 took away a record from the 19th Century (1896 to be exact) and was the first time that cold at National since 1996.
Here is a rundown of February’s amazing records at the three airports:
Sunday, Feb. 8: Record high of 68F ties record set in 1900
Friday, Feb. 20: Record low of 5F bests record of 8F from 1896
Sunday, Feb 15: Record low of 6F bests record of 7F from 1965
Monday, Feb 16: Record low of 6F bests record of 11F from 1963 and 1987
Monday, Feb 16: Record low maximum of 16F beats 22F from 2003
Thursday, Feb 19: Record low maximum of 18F beats 26F from 1972
Saturday, Feb 21: Record snowfall of 8.9″ outdoing 1993’s 2.7″
Tuesday, Feb 24: Record low of -4F bests record of 14F from 1967
Wednesday, Feb 25: Record low of 6F beats prior record of 9F from 1967
Sunday, Feb. 15: Record low of 6F ties prior record set in 1943 and 1899
Monday, Feb 16: Record low of 5F tied with 1905
Monday, Feb 16: Record low maximum of 18F ties 18F from 1904
Thursday, Feb. 19: Record low maximum of 18F beats 19F from 1903
Friday, Feb. 20: Record low of 1F breaks old record of 4F from 1979
Friday, Feb. 20: Record low maximum of of 18F ties 1896
Saturday, Feb. 21: Record low of 2F beats 1885’s 8F
CWG’s Ian Livingston notes another neat fact: This was the second coldest final half of February in D.C. records dating back to the 1870s. The average temperature of 25 degrees ending February 28 fell 0.1 degree behind the same period in 1934 (24.9 degrees). 1885 is now number three with a 25.6 degree average temperature for the end of February.
At Dulles, the average temperature during the final two weeks of February was just 19.5 degrees – easily the coldest on record.
The weather pattern
Like at times in January and frequently last winter, a large area of high pressure ridging over Alaska was most responsible for transporting big cold into the Eastern U.S. On the whole, it was a warm west and cold east pattern with the temperature departure from normal (courtesy of Commodity Weather Group) shown below. Many cities in the Northeast and especially New England are reporting their coldest February periods on record with a number of reporting stations staying below freezing for the entire month.
The upper level weather pattern portrayed in the map below shows the warm Alaska ridge feature. That warm pattern extended from northern Mexico to Alaska to Eastern Asia. The massive ridge offered a wall of resistance preventing warmer Pacific air (and moisture many times) from intruding in a strong north-to-south cold air transport mechanism. Low pressure troughing around the Hudson Bay resided in a classic location to transport cold air from Canada into the Eastern U.S.
For the second year in a row, though, we see a colder-than-normal pattern over Greenland, which is not traditional for cold patterns in the Eastern U.S. High pressure “blocking” (which redirects cold air southward) instead focused again on Alaska. This pattern is fairly rare and while have seen it in other years (Feb. 2003 is an example), we have not seen it as persistent as we have this year and last.
Meteorological winter 2014-15
This winter was 2.7F colder than normal at National, making it the fifth coldest of the 2000s. You can see the overall national winter anomaly map (cold East and warm West) from Commodity Weather Group and the DC temperature rankings here:
There is really no clear upward or downward signal for Washington D.C. winters here in the 2000s (the blue dashed line is the 30-year normal):
For further information
The National Weather Service publishes nice monthly assessments about five days into the start of the next month. You can click on your closest airport location here:
(Capital Weather Gang’s Ian Livingston contributed to this post)