Your light may indeed be the sensor but check the pressure first. When the temperature drops, tire pressure also drops (about one PSI for every ten degrees). The low-pressure light will come on with a drop of 5 pounds, so cold temperatures can trigger the warning light. Driving warms up the tires, raising the pressure and causing the light to go out. Using a simple tire pressure gauge when the car is cold, check and adjust the air in all the tires, including the spare (if you have one). If you still have the issue with the lights, it may be the sensors, which typically last about 7 years.