I was at the parks on Monday and it wasn't crowded at all,I did singles in Mummy with the stand by line at 25 minutes and Shrek had a 15 minute wait.I looked at Rockit running continuously and kept asking if it would open soon and then headed to IOA when it started raining and thundering and saw streams of people heading out of the park.After the rain calmed down I walked around the park with basically everything but SpiderMan closed due to the weather to basically just look at the Potter construction.Now I did go into the parks like at 4pm after being at Sea World to ride Manta in the early part of the day,so maybe Universal was crowded early and the heat scared people away as the day got hotter.