Simply the best advice is to check weather.com before you leave.
Remember also that average temperatures of 61 can mean 50 at night and 70 during the day.
When you see them on sale, buy some cheap gloves. They won't take up much space in your coat pockets, and come in VERY handy when you're waiting for Illuminations by the water.
The lockers in the parks are great for stashing coats when it warms up. OR, you could make sure that the jackets you take can be tied around your waist. (yes, it is not the fashion statement you probably want to make, but it is practical. Besides, these people will never see you again)