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

 

A summer's day in the nation's capital

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.

What does El Nino mean for the hurricane season?

 

Ocean City, Maryland (Photo Credit: Ashley Adams)

Not only have El Nino conditions developed, but NOAA expects them to continue into next year.  That could have significant impacts on the ongoing Atlantic hurricane season.

NOAA’s Climate Prediction Center said yesterday that: “El Niño continues and will strengthen through the end of the year, with a 97% chance it will persist through early spring 2027.” This El Nino could become one of the stronger El Nino’s of recent memory.

El Nino conditions are characterized by warmer than average ocean water in the tropical east Pacific, off the west coast of Mexico. This has global impacts on the weather because El Nino also contributes to below average sea surface temperatures in the tropical Atlantic combined with elevated levels of wind shear. Both conditions tend to preclude tropical development in the Atlantic Ocean.

Consequently, the team of scientists at Colorado State University updated its forecast this week for the remainder of the 2026 Atlantic hurricane season. They’re forecasting a seasonal total of nine tropical storms, of which four become hurricanes with one major hurricane. That’s down from what they were expecting in April (13, 6 and 1).

NOAA issued its seasonal forecast last month that called for 8 – 14 tropical storms, of which 3 – 6 become hurricanes with 1 – 3 major hurricanes. NOAA will update its forecast early next month. A “major” hurricane is a Category 3 on the Saffir-Simpson Hurricane Wind Scale with sustained winds of at least 111 mph.

The three strongest episodes of El Nino over the last 50 years were in 2015-2016, 1997-1998 and 1982-1983. All three saw a commensurate reduction of activity in the tropical Atlantic. It’s important to remember that many factors go into how busy a hurricane season may or may not be. Quiet seasons can still produce damaging and/or deadly storms. For example, Hurricane Andrew in 1992 and Hurricane Alicia in 1983 were the only major Atlantic hurricanes those years and both were exceptionally dangerous. There have also been very active seasons when the United States didn’t see any significant impacts such as in 2010.

The only named storm so far this season was a weak and short-lived tropical storm. “Arthur” developed near the Texas coast last month. The next named storm this season will be “Bertha.”