If we're talking weather, I'd have to say the week I spent in Chicago for opening day 2011. I still had a good time, but it was like 22 degrees the whole week. Very cold, and wet, and probably the most miserable weather I've been in at a baseball game. (The only reason I went that early was because it was literally the only week out of the entire season where the Cubs and Whitesox were in town at the same time.) I remember I got off the red line outside US Cellular Field and there was very thick fog all over the place. Couldn't even see the stadium.