In Washington, when is it illegal to use your high beams?

Using high beams in Washington is illegal when another vehicle is approaching or closely following. This rule is in place to prevent glare that can temporarily blind other drivers, making it unsafe for them to navigate the road. High beams produce a much brighter light that, while helpful for illuminating dark roads, can disrupt the visibility of oncoming traffic. When a vehicle approaches, dimming the lights helps maintain safety for all road users.

While it's generally advisable to switch to low beams on city streets to avoid impacting the visibility of other drivers, the law specifically focuses on the risk of glare in the presence of oncoming traffic or vehicles that are closely following. During the day, high beam usage is less impactful since there's generally more ambient light; driving in the rain often warrants low beams for better visibility anyway, so the primary legal concern remains the interaction with other vehicles on the road.