It's going to be cold and rainy this weekend, what do?

show_the_maw thought this was worth mentioning said
6

All weekend is going to be pretty cold and rainy. My wife is going shopping with her mom which leaves me with the 4 yr old. I was thinking of hitting up the library and maybe the train museum. I was also considering getting a birdhouse kit and putting something together with my little dude. Anyone here have a favorite rainy day activity?