What Do You Bring On A Close-Up DC Trip In April?

In April, I'm going to DC! Well, for school! I'd like to know what to bring... Like what the weather will be like and what to bring on our (Limited to 50 lbs.) suitcase! Yikes! I hope someone has gone before or lives in DC, because, coming from AZ, I need help! Us Arizonans need some help! I'll be sure to p this around to my other friends who are going. I don't know what to do and I need to shop! Hee hee! I also wanted to know about how the hotels are! So, if you know please tell me :D