An air deflector assembly with an adjustable louver for use with a snow plow mounted on a vehicle is provided. The deflector assembly includes a base mounted to the plow, an air scoop detachably mounted on the base and a louver located at the rear of the air scoop. The louver is pivotally secured to the air scoop to deflect the wind onto the vehicle's radiator. A mounting arrangement is also provided to detachably mount the air deflector assembly with the snow plow. The mounting arrangement allows the air scoop and louver to be quickly mounted on and removed from the snow plow.