2019 Rainfall Year-To-Date

NOAA's Precipitation Outlook as August gives way to September

Many DC Area residents know last year was the wettest on record.  The Nation’s Capital had 66.28” of rain in 2018, more than 150% of the annual average of 39.74”.  It also smashed DC’s previous record for wettest year of 61.33” from 1889.  The wetter than average conditions in Washington, D.C. have continued well into 2019.  

Six of the first seven months of 2019 have been wetter than average in the Nation’s Capital.  That’s a higher number of wetter than average months than at the same point last year (five).  However, DC had more episodes of heavier rainfall last year than so far this year.  That makes sense since Washingtonians also experienced a record number of days in 2018 with an inch or more of rainfall (24).

A good example of this occurred in July 2018, which got off to a hot and dry start with no measurable rainfall until July 17.  Ten of the first 16 days of last July also featured 90° heat.  Despite having no measurable rainfall over the first half of July 2018, the month finished with 9.73” of rain (6” above average).  After the dry start to July 2018, it finished with measurable rainfall on seven of the final 10 days of the month.  That frequent rainfall contributed to there being only two days of 90°/+ temperatures during the second half of July 2018.

By comparison, July 2019 finished nearly 3” wetter than average in the Nation’s Capital but had 22 days of 90° heat.  The key difference between July 2018 and July 2019 is that with the exception of July 8, 2019 when 3.44” of rain occurred, there were lots of days with relatively small rainfall totals last month.  In fact, Washingtonians saw rain on 15 of 31 days last month.  

Washingtonians have had below average rainfall so far this month with only 1.97”.  But there will be ample opportunity to add to that total.  The Nation’s Capital averages 2.93” of rain in August.  Weather measurements for DC are made at Nation’s Airport.  Dulles Airport in Sterling, Virginia has had two days with more than an inch of rain since August 1.  That has helped this month become wetter than average at Dulles, but not yet at National Airport.  

Three of the previous four months have been drier than average at Dulles, but only April has been drier than average at National so far this year.  That helps illustrate how spotty late-spring and summer rainfall can be in the DC Metro Area.  Absent tropical systems, rainfall from scattered showers and thunderstorms is often isolated and not all areas see the same amount of rainfall.  Nevertheless, both National and Dulles Airports have rainfall surpluses since January 1.  They just aren’t as large as they were at this point in 2018.