I was driving north on the Kent Black Diamond Rd. I had passed Jenkins Creek and there was farmland to my left. All of a sudden at around 9:50 PM PST, I saw a little white circle travelling between 60 and 120 mph up off in the left part of the sky, my left. It went down in a diagonal, the direction of the letter N, and disappeared. It was not a plane or a reflection. It was too big to be a star, and the edges of it were too well defined, very circular. Bright white like the moon, kind of. It could have been a drone, but why was it going so fast? I was able to estimate the speed of the light because I drove under highway 18 a minute later. The bright circular object was going at least as fast as those cars, maybe up to twice as fast.