You crunching those numbers in Excel or is there a webpage that let's you create those tables?
Two thoughts:
1. Recency Bias. Yeah this would be a warm April pre turn of the century, but look at how many of the last 25 years are ahead of this year at DCA. #1, #2, and #7 are all in the last 7 years! That's what people remember, especially last year.
2. I'd be interested to see the average High / Low for the montth compared to normal. Avg temp only tells part of the story. A gloomy, cloudier than normal spring may have near average temperatures because of lower highs and higher lows. That doesn't mean it'll feel "warm"