What to wear in Boston, MA this summer- going next week July 22, 2009?

Hi, I am gong to Boston, MA next week for the first time. I was wondering what's best to pack with the weather. We'll be staying in the city and plan to tour on foot a lot. As well as do a whale tour, which we hope is a highlight of our trip. I've heard there is a lot of rain this year and it can be humid. I'm thinking shorts for daytime, but how about the evenings with temps in the 50/60's? We're from Texas, so I probably wouldn't do shorts here until we hit mid 60's. I'm also hours away from any bodies of water. So I know those factors can come into play. I am wondering if jeans could get too hot? Thanks for the help!