What condition can make driving visibility significantly low at night?

Driving visibility can be significantly reduced at night due to heavy humidity. This is because high humidity can lead to the formation of fog, which obscures visibility by causing light to scatter. Fog can create a thick barrier that reduces the distance you can see, making it difficult to perceive other vehicles, road signs, and obstacles.

In contrast, clear weather typically allows for the best visibility since there are no obstructions in the air. Windy conditions can aid in dispersing fog and maintaining clearer air, while warm temperatures, especially when combined with clear skies, do not contribute negatively to driving visibility at night. Therefore, heavy humidity is the condition most likely to lead to challenges in visibility during nighttime driving.