Here are my thoughts...
There is a difference between "maintenance" and slacking off.

You can successfully maintain your weight over the summer if that is what you want to do-but you need to practice "maintenance for life" during that time-not slack off because it is summer. Losing control and reversing your lifestyle back to what it once was is a surefire way to gain weight back.
For maintenance, there are two ways that you can go about it:
~You can slightly increase the calorie level that you are currently at. If you are currently at 1400 calories a day, for instance-then go up to about 1600 a day for the summer, or around 200 a day. Since you are not at goal and working towards finding your lifetime maintenance calorie level, increasing it very slightly like this, you might even end up losing 1-3 more pounds over the summer, rather than maintaining it.
~Eat at your regular "lose weight" calorie level that you are currently using to lose weight-BUT-once a week have a "free meal". Not a free day...a free MEAL. Use this once a week pass for 4th of July, a wedding, a family gathering-and so forth-but do so only once a week. If you have multiple events that week, then make a choice which one to splurge at. At the other event, go for ice water/unsweet tea, fresh fruit like watermelon, and other lower calorie summery foods. If you have a treat like a hot dog or a roasted marshmallow-just plan for it and make sure you have the calories to do so at that meal.
I don't like "free days" for this at first-because some can go ape wild and eat everything in sight all day long. A free meal is more limited-because it is one meal per week to splurge.
Either way you choose to maintain during the summer-do not slack off on your exercise. If you go to the maintainers forum, and talk to anyone who has maintained their weight for a long period of time-part of the key is regular exercise. That is work that will always have to be done-no matter if you are losing, or maintaining that loss.