By far, the solar wind wins the prize with a velocity of over 400 kilometers/second at the distance of the Earth. The wind speeds on Jupiter are about 450 kilometers/HOUR. On Saturn they are near 1800 kilometers/HOUR. If I am not mistaken, the upper atmosphere winds on Neptune of 560 meters/second measured by Voyager 2 are the highest planetary winds equal to a bit over 1900 kilometers/hour.