In the second movie Doc gets out of the DeLorean when it's raining and says "wait 5 more seconds" then it stops raining. He then remarks "to bad the post office isn't as efficient as the weather service". Then at the end of bttf2 the Western Union guy says they were given instructions to arrive at that exact location at that exact minute 70 years ago. That's efficiency. Did he know all along what was going to happen?