A cover for a light bar or similar horizontal lamp for vehicles is described. The cover apparatus is equipped with a rear cover portion and a front cover portion. The front cover portion consists of a cover panel configured to pivot to encompass the light within the apparatus, and to be opened at the will of the user to uncover the light bar. The rear half is equipped with one or more heat dissipation vents which conform to standard heat sinks found on conventional horizontal light bars for vehicles. The shape of the apparatus is aerodynamic such that it eliminates audible vibrations known to cause uncovered light bars to ‘whistle’ or otherwise emit an unwanted noise when the vehicle is underway. A version with a stationary, translucent front cover portion is preferred, and is fashioned of a single piece of flexible plastic.