DC’s historic July 4 heat wave

 

Torrid early July weather in the DMV

This month’s weather has gotten off to an historic start in the nation’s capital. For only the eighth time on record, Washingtonians experienced three consecutive days of triple-digit heat. Multiple record highs were set, including the hottest July 4.

Two of the three record highs that were broken had been over 100 years old. That helps underscore how unusual the heat wave was in the DMV (DC, Maryland and Virginia). Unfortunately, it coincided with the July 4 holiday when so many folks had outdoor plans. However, that served as an important reminder to remember hot weather safety tips (limit your time outdoors, drink plenty of water, use suntan lotion, etc.). 

The 2026 summer has gotten off to an exceptionally hot start in the nation’s capital. If no more triple-digit heat were to occur this summer, Washington, D.C. would finish with four days of it (including the June 12 record high of 100°). That would allow 2026 to tie for DC’s sixth highest annual total on record. That’s remarkable since official NOAA weather records in the nation’s capital date back to the 1870s.

This was also the fourth stretch of three or more consecutive days of triple-digit heat in the nation’s capital just since 2010. What makes these four stretches stand out even more than the four that occurred last century [1993, 1988, and 1930 (2)] is the more pronounced urban heat island effect that’s developed in Washington, D.C.

The urban heat island effect has helped overnight low temperatures remain warmer than they used to when urbanization, vehicular traffic, and greenhouse gas emissions were lower than present levels. For example, the average daily high/low temperatures in the nation’s capital during the four stretches of triple-digit heat of three or more days in the 1900s were 101.1°/76.5° while the four this century were 101.6°/79.5°. The average daily overnight low temperature during this century’s streaks were 3° warmer than the equivalent periods last century.

Intense heat waves have also occurred more frequently in the nation’s capital this century with four stretches of at least three consecutive days of triple-digit heat in the last 14 years vs. four between 1930-1993.

July 1 record high / record high-low (Source: NOAA)

IAD: 97° (old record: 96° - 2012) / 73° (old record: 72° - 2017, 2014)

July 2 record highs / record high-lows

DCA: 102° (old record: 101° - 1898) / 80° (old record: 79° - 2012, 1872)
IAD: 98° (old record: 98° - 1966) / 75° (old record: 75° - 2022)

July 3 record highs / record high-lows

DCA: 102° (old record: 101° - 1966, 1873, 1872) / 84° (old record: 80° - 2018)
IAD (record high-low): 78° (old record: 73° - 2018, 2006)

July 4 record highs

DCA: 103° (old record: 100° - 1919)
IAD: 99° (old record: 97° - 2002, 1999)
BWI: 102° (old record: 2002, 1966, 1898)

Years with most days of 100-degree heat in Washington, D.C. (Source: NOAA)

11 – 1930
8 – 2012
7 – 1988
6 – 2024, 1980
5 – 2011, 1997
4 – 2026, 2016, 2010, 1993, 1954, 1871

Weather Quiz

 

View of Georgetown from Roosevelt Island

True or False. 

Seven of the 10 warmest July’s in the nation’s capital have occurred since 2010.

Remembering DC’s most extreme heat waves

 

Excessive Heat Warnings on July 3, 2026 (Source: NOAA)

DC’s highest number of consecutive days with triple-digit heat is four. That’s happened three times since official NOAA weather records began in the 1870s. There has been another four instances that triple-digit heat occurred on three consecutive days. Today could be the second of three consecutive days of triple-digit heat in Washington, D.C.

2024: The signature event of DC’s third hottest summer occurred from July 14 – July 17. For only the third time on record, the nation’s capital experienced four consecutive days of triple-digit heat. DC’s average daily high/low temperatures during these four days was 102°/79.5°. The hottest day was July 16, my birthday, with a record-tying high of 104° and a low temperature of 80°. Triple-digit heat occurred in June, July and August that summer for the first time in the nation’s capital since 2011.

2016: DC residents sweat through its fourth hottest summer a decade ago. The hottest stretch of weather occurred from August 13 – August 15 with three consecutive days that high temperatures reached 100°. This was DC’s first stretch of three or more consecutive August days of triple-digit heat since 1930.

2012: Those living in the DMV (DC, Maryland and Virginia) at the time will remember this summer for the infamous June 29 derecho and the extreme heat that followed. What made the intense heat even more dangerous was that many DMV residents lost power for up to a week after the derecho. That meant no air conditioning during a dangerous 11-day heat wave. The hottest stretch of triple-digit heat was on July 5 – July 8 when DC’s average daily high/low temperatures were 101.8°/80°. The hottest day was July 7 with high/low temperatures of 105°/82°.

1993, 1988: Each of these July’s saw a stretch of three consecutive days of triple-digit heat in the nation’s capital. DC’s hottest day in 1993 was July 10 with a high/low of 100°/81° while in 1988 it was July 16 (104°/77°).

1930: This year produced DC’s highest number of 100-degree days (11). Six of those 11 days occurred that July, including four consecutively from July 19 – July 22. The hottest day was July 20 when DC had high/low temperatures of 106°/76°. In fact, that was one of only two times the nation’s capital was at hot as 106°, along with August 6, 1918. DC’s average high/low temperatures during this four-day period were 102.8°/75°. 

How unusual is triple-digit heat in the nation's capital?

 

DC's 7-day forecast (July 1, 2026: The Weather Channel)

The nation’s capital is poised to experience one of its most intense heat waves in recent memory. High temperatures could reach or exceed 100° on four consecutive days starting this afternoon. Since triple-digit heat is so rare in the nation’s capital, having multiple consecutive 100-degree days would be an historic event. 

July is typically the hottest month of the year in the nation’s capital. As such, it isn’t surprising that triple-digit heat occurs most frequently in July. This century, Washington, D.C. has averaged one day of triple-digit July heat every other year, one such day every third August and one June day of triple-digit heat roughly every five to six years. This summer has already had one 100-degree day with a high of 100° on June 12. 

Triple-digit heat also tends to be feast or famine in the nation’s capital. For example, before the summer of 2024, that had six days of triple-digit heat, there hadn’t been any since 2016. The month with the highest overall number of 100-degree days in the nation’s capital remains July 2012 (7). However, the summer with the most 100-degree days remains 1930 with 11.

A heat wave is loosely defined as a minimum of three consecutive days that high temperatures reach at least 90-degrees. There have been multiple heat waves in the nation’s capital that didn’t have any triple-digit heat. The most notable such heat waves that occurred recently were a 12-day stretch in July 2019 and a 20-day stretch in 2020. However, while those heat waves were known primarily for their longevity, the upcoming heat wave will be known more for its intensity.

The typical summertime weather pattern in the United States is conducive for heat waves in the DMV (DC, Maryland and Virginia). That's when a semi-permanent area of high pressure sets up off the southeast coast of the United States. It's sometimes referred to as the "Bermuda High" since that's where they are often centered. The clockwise winds around this seasonal area of high pressure usher hot and humid air northward from the deep south into the Mid-Atlantic Region.

Tomorrow and Friday, July 2 and July 3, are setting up to be the hottest days in the DMV. That’s when temperatures are most likely to reach the triple-digit mark.

Longest streak of consecutive 100-degree days in Washington, D.C. (Source: NOAA)

Four Days

July 14 – 17, 2024
July 5 – 8, 2012
July 19 – 22, 1930

Three Days

August 13 – 15, 2016
July 8 – 10, 1993
July 15 – 17, 1988
August 3 – 5, 1930