Is triple-digit heat common in the nation’s capital?

Bishop's Garden, Washington National Cathedral

The nation’s capital can experience triple-digit heat in June, July, August, and September. The earliest in the calendar year Washington, D.C. has experienced 100-degree heat is June 5, while the latest it’s occurred is September 8. Triple-digit heat is more common in some months than others.

June: Historically, there’s been a total of 17 days of June triple-digit heat in the nation’s capital. June 9 is when Washington, D.C. has seen the highest daily total of 100-degree days (three) since weather records began in 1871. The hottest June temperature on record is 104° set on June 29, 2012. Triple-digit heat has occurred on consecutive June dates only once: June 29 – June 30, 1959.

July: It’s not surprising that the hottest month of the year has seen the most days of triple-digit heat with 68. 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 five days of triple-digit heat. The nation’s capital had the highest number of July days with triple-digit heat in 2012 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.

September: Average daily temperatures and length of daylight decrease significantly in the nation’s capital in September. As a result, September has seen the lowest total (four days) of triple-digit heat, with none since 1980. September’s hottest overall temperature of 104° occurred on September 7, 1881. The latest in the year triple-digit heat has occurred was on September 9 (100° in 1939).

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 2011, July 2010, July 1980, July 1953, August 2016 – 3