We went last year, the first week in June. This was our first trip so I have nothing to compare lines to but I didn't think the lines were bad at all. The longest we waited was for Soarin and that was about 35 minutes without a FP. We did sit for about 25 minutes for the Voyage of the Little Mermaid but that was our choice because it was hot and we needed a break. I think we waited longer for the busses when we were leaving the parks for the day then we did any ride.
As for the heat, we had some really nice days and some really super hot days. It rained only one day on our trip and it was a brief 15 minute shower. It happened to occur on our second day when we were just entering MK, so we walked into a shop and looked around until the rain let up and went on about our day. On our 5th day, we went to DHS and it was H O T. We just took plenty of breaks and when the kids said they were too hot and wanted to call it for the day, we did.
Outside of TSM, we never saw a line over 1 hour. We're from Ohio and go to Cedar Point frequently so waiting an hour or more is nothing to us, so we were surprised when we heard people say "I'm not waiting 25 minutes for X". Heck that's not a wait if you as us