A closer look at some of DC’s impressive July rainfall

 

A rainy July 2019 day in Rockville, Maryland (Photo Credit: Susan Granzow)

NOAA’s (National Oceanic and Atmospheric Administration) current 30-year average temperature and precipitation totals for the United States reflect the period of 1991-2020. Since this period was appreciably warmer and wetter in the nation’s capital than the previous 30-year period of 1981-2010, there were significant changes. 

July saw the most significant changes in the updated data set. Previously, July was DC’s third wettest month of the year with an average of 3.73” of rain. However, July is now the wettest month of the year in the nation’s capital with a new monthly rainfall average of 4.33”. 

Here’s a look at recent rainy July’s in the DMV (DC, Maryland and Virginia).

2024: Although this July is remembered for its extreme heat, it also had very wet weather. The four-day period of July 22 – July 25 had two days with more than an inch of rain in the nation’s capital (July 22: 1.57”; July 25: 1.28”). While not record-setting, these impressive daily rainfall totals helped the month finish with above average rainfall.

2022: This July continued the recent trend in the nation’s capital for exceptionally wet days. A total of 4.05” fell on July 9, which was DC’s fifth wettest July day. To add to that, a daily rainfall record was set merely a week later on July 16 with another 1.38” when thunderstorms passed through the DMV.

2020: The monthly rainfall total of 6.51” was above average. What made this July significant was that 60% of the monthly rainfall occurred on just two days. A daily rainfall record of 2.04” occurred on July 7, while another 1.89” fell on July 23.  

2019: This July got off to wet start with measurable rainfall on five of its first eight days. The signature rainfall event was on July 8 when a daily rainfall record of 3.44” occurred at National Airport. That accounted for more than half of DC’s monthly total of 6.49”. Most of that rain fell in less than two hours, snarling the morning commute across the DMV.

2018:  An impressive total of 4” of rain fell at National Airport on July 21 that set a new daily rainfall record. Moreover, 8.52” of rain fell during the eight-day period from July 17 – July 24. It finished as the fourth wettest July in the nation’s capital with 9.73”.

2017:  This July finished with 9.15” of rain, making it DC’s wettest since 1969. During an eight-day period from July 22 – July 29, a total of 6.15” of rain fell. The wettest day of the month was on July 28 when a daily rainfall record 3.31” was recorded at National Airport.

Weather Quiz

 

A sultry summer's day in Washington, D.C.

What is the hottest temperature on record in Washington, D.C.?

A. 103°

B. 104°

C. 106°

D. 108°

   

A closer look at triple-digit heat in Washington, D.C.

 

A stellar summer day in Washington, D.C.

The nation’s capital has experienced triple-digit heat as early in the year as June 5 and as late as September 8. However, triple-digit heat is more common in some months than others.

This month has already seen three days of triple-digit heat. That’s tied July 2026 for DC’s fifth highest monthly total. Making this month’s triple-digit heat even more unusual is how it occurred on three consecutive days. High temperatures today and tomorrow will be on either side of 100° in the nation’s capital.

The nation’s capital has seen a total of 18 days of triple-digit June heat since official weather records began in the 1870s, the third highest monthly total behind July and August. The most recent such occurrence was just last month on June 12. September has seen only four days of triple-digit heat in the nation’s capital with none since 1980. 

July: It’s not surprising that the hottest month of the year has seen the most days of triple-digit heat with 71. All but three July days have had triple-digit heat (July 11, July 12 and July 30). Three other July days (July 16, July 17 and July 21) have seen a combined total of five days of triple-digit heat. July 2012 holds the record for most days of triple-digit heat of any month in the nation’s capital with seven.

August: There’s been a total of 34 days of 100-degree in August since weather records began. Washington, D.C. had its highest number of August days (five) with triple-digit heat in 1930. The second highest monthly total (three) occurred in 2016. The District’s hottest overall temperature of 106° has occurred twice, on August 6, 1918 and July 20, 1930.

Months with the most 100-degree days in Washington, D.C. (Source: NOAA)

1. July 2012 – 7
2. July 1930 – 6
3. August 1930 – 5
4. July 2024, July 1993, July 1988 – 4
5. July 2026, July 2011, July 2010, July 1980, July 1953, August 2016 – 3

Beware July hurricanes

 

Hurricane Beryl, July 2024 (Source: NOAA)

The tropical Atlantic often sees an uptick in tropical storm and hurricane development in July as atmospheric and environmental conditions become more favorable. Although not as frequent as in late-August or September, there have been destructive July hurricanes.

Beryl (2024): Hurricane Beryl reached peak intensity on July 2 as only the second Category 5 storm to develop in the Atlantic in July. It highest sustained winds were 165 mph and its lowest minimum central air pressure was 932 millibars (mb). Standard sea level air pressure is 1013 mb. It was the earliest Category 5 Atlantic hurricane on record, breaking Hurricane Emily's 2005 record by two weeks. When Beryl first reached Category 4 status on June 30, it broke another 2005 record for earliest Category 4 storm.

Chris (2018): While not particularly strong or destructive, I’m partial to mentioning my namesake storm. “Chris” first appeared on the list of names for Atlantic tropical systems in 1982.  It has been a named storm every six years since then and was a hurricane three times. The most intense version occurred eight years ago when it reached peak intensity as a Category 2 storm on July 11, 2018, with sustained winds of 105 mph. Fortunately, it was a safe distance off the East Coast and didn’t have any major impacts on the United States.

Arthur (2014): Hurricane Arthur menaced beach-goers in North Carolina over the July 4 holiday 12 years ago. The first named storm of the season, Arthur also became the earliest landfalling North Carolina hurricane on record. At peak intensity, Arthur was a Category 2 hurricane with sustained winds of 100 mph and minimum central air pressure of 973 mb. It made landfall near Cape Lookout, North Carolina early on July 4. Although damage was relatively minimal, it forced holiday travelers to leave early or postpone their travel plans altogether.

Bertha (2008): Bertha had sustained winds of 125 mph and a minimum pressure of 952 mb at peak intensity. Fortunately, it never made landfall and remained over the open Atlantic Ocean.  But it was a long-lasting system, having been a tropical storm or hurricane from July 3 – July 20.  That made Bertha the most protracted July tropical storm or hurricane on record in the Atlantic Ocean.

Emily (2005): The 2005 Atlantic hurricane season was a record-setting year that saw the first Category 5 July hurricane on record. Hurricane Emily briefly reached Category 5 strength on July 16 with sustained winds of 160 mph and a minimum air pressure of 929 mb. Fortunately, Emily caused only minor damage in southern Texas.