Unfortunately, the engine has to be running in order for the A/C to operate--however, there are some things you can do to help avoid excess heat in the car. one way is to open all your windows partially, so that some heat can escape. There are also fans that are designed specifically for the car, and operate using the car's battery. I saw one of these at Target just the other day. They also have clip-on fans that you can clip on just about anywhere--your car, your clothing, anywhere. And these do not run off the car battery--regular batteries should do just fine.