100+ degree days in DC: 21 in 1930, but only four so far in 2010?

It looks to me like DC reached 100 degrees once in June, three times in July, and zero days so far in August.  As of August 17, I see none in the 10-day forecast.   How likely is it that DC will reach 21 100+ days this year, as it did eighty years ago?

Tom Russell's Blog : It was Hot, But not That Hot...

During the Summer of 1930, 21 days were 100 degrees or above in Washington DC.