Last year, as others have said. The last time we had the situation we see this year was 2020, which had 46 days of 90+ and 42 days of 32 or below. 2019 had 47 days of 32 or below and 62 90+ days (one of the highest on record).
This year is remarkable though, with only 24 days with freezing temps (I don't think that includes today - so make it 25). From what I can see that is the lowest on record for DCA, with the next closest being 28 days in 1969. We'll see if we break that record.