We went last April 12-19. We were so unlucky in that it was a cold front that came through the first few days we were there. It was about a high of 75 during the day. We did only get rain for one day, but it was FREEZING because it was already cold out. Nighttime I swear it was like 55 degrees! We were so cold a couple of nights! Then the last two days we were there it was almost 90.
Anyway...I would suggest you pack shorts and shortsleeve shirts, but pack 2 pair of jeans and a couple of sweatshirts too. Just incase. I'm sure glad we did that! Of course check the weather forecast the day before you leave. That'll give you a pretty good idea.
Have an awesome trip!!