When there is no fog but you want other drivers to see you.
When you're in a hurry during the day.
When visibility is poor due to fog.
You should use your vehicle's fog lights when visibility is poor due to fog. Fog lights are specifically designed to illuminate the road immediately in front of your vehicle in low visibility conditions, helping you see better and making your vehicle more visible to other drivers. Using them in other conditions, such as at night or when there is no fog, can be distracting to other drivers and may not be legal.