In BC you can run your fog lights at any time, you just cannot run them instead of headlights unless "atmospheric conditions make the use of headlights disadvantageous.

Fog lights may be operated at any time, but when they are on, park, tail, license and clearance lamps (if any) must be lit also. Fog lights may be used in place of headlamps when atmospheric conditions make the use of headlights disadvantageous. That might not be during night, but is most likely.

Fog lamps

4.11 (1) A motor vehicle may be equipped with 2 fog lamps, mounted on the front of the vehicle below the headlamps, that are capable of displaying only white or amber light.

(2) Each fog lamp must be

(a) mounted not more than 30 cm below the headlamps, and

(b) adjusted and aimed so that, at a distance of 8 m from the lamp, the centre of the beam is at least 10 cm below the height of the fog lamp.

(3) The fog lamp wiring and switch must permit simultaneous operation of the parking lamps, tail lamps, licence plate lamp and, if required, clearance lamps.

(4) The operator of a vehicle may use fog lamps instead of headlamps when atmospheric conditions make the use of headlamps disadvantageous.