1980 and 2010 were remarkably similar. Both ended up with 67 days of 90+. 1980 has 5 100s and 2010 had 4. The average high for the days that hit 90 were within a fraction of each other. In 2010 the heat started early with a couple of 90s in the first week of April, while in 1980 it stretched on with 14(!) 90+ days in September. 1980 did have the 21-day 90 streak which I believe still lives as the longest.
Here's my disturbing heat stat, though. Only 4 years in the entire DCA climo record have had 4+ days where the total temperature (high + low) is 180, or a 90.0 average.
2011
2012
2016
2024