RodneyS

Breaking news -- literally. With 2.76 inches of precipitation already recorded at DCA today and 3.57 so far for September 2018, the previous May-September DC record total of 32.26 inches set in 1934 has now been exceeded, at 32.43 inches. Let's see how high we go by September 30th.

August 2018 continued the rainy trend at DCA, at 5.19 inches. That brings the May-August 2018 precipitation total there to 28.86 inches, tied with May-August 1878 for second on the all-time DC list, behind only May-August 1886, at 30.41 inches.

DCA _ NYC _ BOS ___ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA 2.6 3.0 3.1 4.2 1.0 0.8 1.8 1.0 -0.3

The beat goes on. This year, DCA recorded 0.36 inches of precipitation on August 12th and nothing on August 15th. So, the updated totals, 1871-2018, are: August 12: 43.43 inches total; 21 days with a trace, 54 days with measurable, 12 days with at least an inch, 5 days with 2+ inches. August 15: 12.45 inches total; 16 days with a trace, 47 days with measurable, 5 days with at least an inch, no days with 2+ inches.

While DCA could not match BWI's record-breaking July 2018 precipitation, the 9.73 inches recorded there was 4th on the all-time DC July list, and the most since the record 11.06 inches in July 1945. Also, the May-July 2018 total of 23.67 inches at DCA was third on the all-time list for those three calendar months, and the most in 129 years. Only May-July 1889, at 23.83 inches, and May-July 1886, at 27.98 inches, had more precipitation in those three months.

DCA _ NYC _ BOS ___ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA 1.0 1.7 2.9 2.2 -1.3 -0.1 1.7 -0.9 -0.1

And May 2018 has the distinction of being an exceptionally warm, and yet still rainy, month in DC. Average temperature of 72.4 degrees at DCA places it third on the all-time DC list behind only 2015 (73.2) and 1991 (73.0). Further, the warm-up from April 2018 was 17.5 degrees, second only to April-May 1911 (18.8 degrees). And yet precipitation was 8.73 inches, which is 6th on the all-time DC May list (May 1953 is # 1, at 10.69 inches).

You're on to something. May 12-19, 2018 was indeed the first time in DC weather history that eight straight days each recorded at least 0.15" of precipitation. The previous record for that amount or more was seven straight days, set in July 1938 and equaled in July 1941; see http://xmacis.rcc-acis.org/#. Click on that link, then select "Single Station" and click on "Consecutive Days." For "Criteria" select "Precipitation" then type in (more or equal to) "0.15." Then select the "Washington Area" station and click "Go." As I just posted to an article on the Washington Post's Capital Weather Gang: "Rainy to be sure, but to put things in perspective, DC's record single-day rainfall is 6.39 inches, on August 23, 1933. More recently, DCA recorded 9.08 inches during the five-day period September 22-26, 1975."

I have just discovered that the above statement is not true for 0.4", as only 2011, 1975, and 1937 also had 5-day streaks of at least 0.4 inches. However, I would have thought that the statement would have more logically read: "It has been an unusually wet pattern over the last week. For DCA (Reagan National), there has been at least 0.4" of rain each of the last 7 days. This is the longest streak on record. The previous longest was 5 days in 2011, 1975, and 1937. Precipitation records date back to 1871."

You can view the May 2018 daily precipitation totals at DCA here under "Preliminary Monthly Climate Data" (Column 7 "WTR")-- https://w2.weather.gov/climate/index.php?wfo=lwx

The week of Sunday, May 13, 2018 through Saturday, May 19, 2018 saw at least 0.4 inches of precipitation at DCA each of those seven days. Previously, no more than five consecutive days in DC weather history recorded at least 0.4 inches each day.

February 2018 at DCA was not as warm as last year's record-setter of 47.7 degrees, but its 45.3 degree average was good enough for 3rd place all-time in DC, behind only last year and February 1976 (46.9). The warm finish to the meteorological winter brought the 3-month average to 40.0 degrees, with a true 90-day average of 39.9. Each average was 3.9 degrees below last year's respective averages, but still warm enough for the 29th all-time warmest meteorological winter in DC.

Today made it to 82 at DCA and 80 at IAD, for the earliest 80+ readings at both airports. The 82 at DCA was 34.7 degrees above the 1872-2017 average of 47.3 for February 21st in DC. I believe that ties today with March 22, 1907 for the 4th largest maximum departure in DC history. The latter day reached 90 degrees, relative to the 1872-2017 average of 55.3 for March 22nd in DC.

You're welcome. By the way, the 84-degree February reading in 1930 was actually on the 25th. Relative to the long-term (1872-2017) average maximum for February 25th in DC of 48.7 degrees, that represents a departure of 35.3 degrees, which is 3rd on the list of maximum departures in DC history. Second is January 26, 1950, whose 79-degree maximum represents a departure of 36.1 degrees from the historical average maximum of 42.9 degrees for January 26th. And number one on the list is March 23, 1907, whose 93-degree maximum represents a departure of 36.6 degrees from the historical average maximum of 56.4 degrees for March 23rd.

No, Topper is correct. The most memorable thing about the 1997-98 El Nino was a run of eight straight 60+ readings at DCA between January 2-9, 1998. However, the maximum was only 69 on January 8th. In fact, we did not reach 80 until March 27th of that year, when the maximum was 81.

Today's high of 77 at Dulles was the warmest ever for this early in the year. At DCA, on the other hand, today's high of 78 set a new record for today, but came up short of the 79 recorded on both January 26, 1950 and February 17, 1976.

Yesterday and today marked the first time since April 29-30, 2014 that DCA recorded consecutive days with at least one inch of precipitation. Also, during the first 11 days of February, DCA recorded more precipitation (3.78 inches) than it recorded during November 2017, December 2017, and January 2018 combined (3.44 inches).

For a nearly "normal" temperature month at DCA, January 2018 was quite interesting. While the average temperature of 35.7 degrees was only 0.3 below the 1981-2010 normal, the standard deviation of the 31 daily averages from the monthly average was 12.7 degrees. That's the highest standard deviation for any month since February 1996, which was 13.1 degrees (highest ever for DC was the lengendary month of February 1899, which was 15.6). Further, January 2018 precipitation was only 0.94 inches at DCA, the fourth lowest in January in DC behind only 1948 (0.31), 1872 (0.35), and 1981 (0.38). Moreover, for the five months ending in January 2018, precipitation totalled only 6.89 inches at DCA, the third lowest for that period in DC behind only September 1930-January 1931 (5.43) and September 2001-January 2002 (5.50).

February is normally relatively dry at DCA, although January is normally drier on a per day basis (average of 28.25 days in February vs 31 days in January). However, the last five months have been abnormally dry at DCA, with total precipitation totalling under 7 inches since September 1, 2017. Assuming that we receive no more than an inch or so between now and Wednesday, precipitation during September 2017 through January 2018 will be the third lowest total in DC for any September-January period (147 year record), behind only September 1930-January 1931 (5.43 inches) and September 2001-January 2002 (5.50 inches).

According to my records, yesterday's 41-degree temperature spread at DCA (62 maximum, 21 minimum) was the greatest since December 22, 1998 (67/24).

I just noted on the Capital Weather Gang discussion board that Kevin Benedict corrected one of my statements. The 13 days January 9-21, 1994 were slightly colder than the 13 days January 11-23, 1994 (21.2 vs. 21.8), and so our most recent 13 days came up 0.4 degrees shy of the coldest 13 consecutive days of January 1994. Also, January 9-22, 1994 averaged 21.6 degrees vs. 22.0 during January 10-23, 1994, and so our most recent 14 days came up 0.9 degrees shy of the coldest 14 consecutive days of January 1994. It is interesting to note, however, that while we came up just shy of beating the 13- and 14-day January 1994 cold streaks, we did surpass the coldest 13-day streak of January 1977 (January 11-23), which averaged 21.9 degrees at DCA. January 1977 was the 5th coldest January in DC history, at 25.4 degrees, compared with 28.8 degrees for January 1994, but it wasn't as intensely cold for any 13-day period.

As best as I can tell, the two weeks ending today at DCA are the coldest in nearly 24 years. Specifically, December 26, 2017 through January 8, 2018 averaged 22.5 degrees, and I can't find a colder two-week period since January 10-23, 1994, which averaged 22.0 degrees. That cold snap was highlighted by one of the coldest days in DC history-- January 19th -- which saw a maximum of + 8 and a minimum of -4, which was the last sub-zero reading at DCA. Moreover, if only the most recent 13 days are considered (December 27th to January 8th), the average was only 21.6 degrees, which was lower than the coldest 13 days in January 1994 (21.8 average during January 11th through 23rd). To find a colder 13 days than the most recent 13, you need to go back to December 15-27, 1989, which averaged 20.5 degrees.

Dulles fell below zero this morning for the first time since February 24, 2015. This morning's reading of -1 broke the record for January 7th of +1 that was set in 2014.

December 2017 at DCA came in at 39.2 degrees (0.5 below the 1981-2010 normal), and 2017 averaged 60.8 degrees, displacing 2016 (60.3) as DC's second warmest annual average temperature, behind 2012 (61.5). Similarly, December 2017 at IAD came in at 35.0 degrees (1.6 below the 1981-2010 normal), and 2017 averaged 57.2 degrees, again displacing 2016 (57.1) as IAD's second warmest annual average temperature, with 2012 again remaining the warmest (57.9).

Looks to be pretty much a done deal that 2017 will displace 2016 as second warmest in DC, despite the forecast of below normal December temperatures. As long as the DCA December temperature lands in a range of 34.2-47.3 degrees, 2017 will average in a range of 60.4-61.4 degrees. 2012 will remain warmest at 61.5 degrees. IAD also may finish 2017 as the second warmest, but that's more uncertain, as it would have to average between 34.3-43.5 degrees in December. The December average temperature there might fall below 34.3 degrees, and thus 2017 would fail to displace 2016 as the second warmest.