Interior Rearview Mirror problems of the 2006 Buick Lucerne

When driving in the rain my Buick Lucerne's exterior driver-side rear view mirror is useless due to the wash of water streaming across the driver's side window. It is impossible to see traffic in the left lane and in order to change lanes I must rely on the interior rear view mirror. This loss of visibility occurs whether or not there is a wind condition, but it is most dangerous on the highway at highway speeds with windshield wipers pushing water toward the driver side window. I have had a couple of near misses during daylight driving conditions.