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