The weather in Washington DC is pretty average for the U.S. It has four distinct seasons and for a few weeks in the summer it can get quite muggy. Mid July through mid August, you definitely want to be prepared for some hot and sticky daylight hours (into the 90's). In the winter, it rarely gets too far below 30 degrees and in the spring, the flowers and the cherry blossoms are beautiful. The fall is one of my favorite times to visit this city. I like the The fall colors, the nip in the air make walking through the district a lot of fun.