May is usually very nice, I have been when it is warm enough for shorts and a t-shirt but not hot and it has also been quite hot. Well, hot for us and we don't really get that hot like you guys on the other coast.
When are you going in May?
Weekends are always busy but it is also the only time to see the fireworks.
Memoiral weekend will be quite busy too!
I just found out about the lack of fireworks during the week! So sad! I am there for my birthday (as well as my best friend's birthday) on May 5th and 6th.
We were the week of Mother's day last year. Low crowds except for weekends, but it hit 105, so very hot..Thank goodness for the pool and play area in DCA.