Q: Hydraulic brake booster warning light and buzzer will sound after car has been sitting in extreme cold. Turns off after car warms 2004 Lexus LX470

The car had been outside all day (Chicago winter) and as we began driving home, the break light came on and a buzzer began to sound. It did not come on until about 5minutes or so into driving time. We pulled over and pulled and turned off emergency break, turned car off and on. None of these things helped. Breaks were functioning normally so we continued driving. After about 10 minutes or so, the buzzer stopped and the light went off. The next morning, this did not happen again but, the car had been in our garage overnight. When my husband got into his car at the end of the day, after the car had been sitting exposed at the train station all day, it happened again. Same thing yesterday. Fine in the morning after being in the garage overnight, but buzzer and light in the evening after sitting at the train station. The breaks feel normal (no stiffness etc). It is bitterly cold here right now with consistent temps and wind chills below zero.