That snowflake-shaped light on your 2000 Mercury Cougar's rearview mirror indicates that the
outside air temperature is below a certain threshold, and the car's system has detected conditions that could lead to ice or frost formation. It's essentially a warning about potentially hazardous driving conditions due to cold temperatures.
You can't turn the light *off* directly. It's an indicator light, not a switch. The light will go out automatically once the outside temperature rises above the threshold the car's system is programmed to detect.
