A couple things also to remember, as people said, It could be 70 or 80 during the day, but 50-60 at night. Also pay attention to weather it's cloudy or not, clouds during the day may keep it cooler, but at night they keep the heat in. Also realize that you're in the park with 40,000 or more people, and that creates body heat. It will honestly colder waiting for the tram, and in the esplanade then it will be in the parks. I would honestly say that it's about 5 degrees warmer in the parks with all the body heat than it is outside the parks. I wouldn't bring a heavy jacket unless it's in the 40's and windy. I've learned that most times a long shirt and sweatshirt are more than enough even during the winter, and I'm a wimpy SoCal boy that needs to bundle up!