hey, I have an acura 3.2 cl and primarily its just a suped up honda. anyway i have had a similiar problem with the brake light illuminating in cold temps. any where between 50 to minus 10 degrees. ( i live on the east coast) Usually what caused my problem was the float in the main brake reservoir just sticking to the side of the reservoir container. To alleviate the problem i just simpy slid the float up and down the shaft a couple of times and that was the fix. I havent has any problems with the brake light illuminating since. I think the brake fluid may have a little bit of moisture freezing the float inside the reservoir. I know water is not supposed to be in there but thats all i could think of. Hope it helps