91 Regal brake lights on when cold

When it has turned cold, the brake lights on the buick come on. By "pulling" the brake pedal they go off. But since it is getting colder earlier, the battery has run down and jumping is required. what causes this and how to fix?

there is a switch on the brake pedal connecting rod. it controls the brake light. when ever its pressed, light is off. when its released, the light turns on. that switch may need adjusted. simple job,just loosen the screw, move it, tighten the screw. only hard part is most of the time you need sit in the driver's seat upside down with you feet in the air to get a good look at it.