On Tuesday, record rainfall visited the area yet again as both Washington and Dulles set daily records, with well over two inches of rain at both locations. Thanks to the parade of heavy-rain events, many locations in the region have notched above-normal rainfall for August and the summer overall. Impressively, some — including the District — have reached or exceeded their average yearly rainfall amounts, as well, with a third of 2018 still to come.
Tuesday’s daily record of 2.46 inches in the District came from multiple rounds of storms. It was the largest August daily total since 2011 and the 26th-rainiest August day on record since 1871.
The downpours pushed the August rainfall total in Washington up to 4.83 inches. This is 1.9 inches above the normal of 2.93 inches for the entire month. While the monthly total is indeed high, it is not quite approaching historic territory. But the combined July-August total of 14.56 inches ranks as the 10th-wettest such two-month stretch in D.C. history, and the wettest since 16.42 inches fell during these two months in 1969.
It’s a similar story in Washington’s western and northern suburbs, where Dulles picked up 2.72 inches of rain Tuesday, a daily record. Dulles is at 4.53 inches for the month, compared with a normal of 3.53 inches.
After being socked by deluges in July, Baltimore has missed some of the major downpours in recent days, so it is only closing in on the monthly normal, with 2.9 inches to date in August. However, the two-month period is the wettest July and August on record for that city. Radiant Solutions, a weather consulting group, pointed out that the city is also closing in on its wettest summer on record.
The rounds of rain and flash flooding Tuesday presented another reminder that 2018 has featured both gullywashers and full-day washouts.
Tuesday marked the District’s 15th day with at least one inch of rain this year. That puts it in a tie with 1878 for the second-most number of such days to date on record. The top year was in 1886, when there were 18 such days to date. Astute observers will note that both of those former totals were observed downtown vs. rainfall now measured at Reagan National Airport. This year’s 15 one-inch-plus rainfall events at National are the most on record to date, surpassing 1948’s 14 such cases.
For all of 2018, Washington’s total rainfall of 39.74 inches so far ranks as the sixth-most on record. That’s more than 14 inches above average through late August, and — oddly enough — exactly the current average for a full year. In Baltimore, the 44.38 inches to date is two inches behind Baltimore’s wettest year to date: 1889.
Impressive rain totals in mind, it remains a bit early to speculate about achieving historic rainfall totals for the year in Washington. September and October, in particular, can be very wet or quite dry. Given the lack of any significant tropical systems in the Atlantic Ocean, and a continued environment that is more hostile to development than normal, dry may be somewhat favored once we get out of this wet summertime pattern.
Because of the tremendous amount of rainfall in July, Baltimore does seem likely to crack the top 10-wettest for annual total and, perhaps, considerably higher. Adding in just average rainfall for the final four months to the current tally would place the resulting total safely in the top five all-time wettest. Hopefully, we can dry out before running the totals up further.