It turned out to be an incredible experience. It was, well, PRIMAL! Just me, my and two K-9 running buddies (the German Shepherds who always come with me), running the trail through the darkness. The trail I was on is one well known to me. I don't know if I would try a new route under those conditions, but this was one of the most enjoyable runs I have had in a long time. This time of year the sun is coming up later, so we had a good hour of real darkness. The fog also muffles much of the sound, so we ran through the dark, hearing the water dripping off of the leaves of the oak trees as it collected from the fog.
I purposely made this one a slow run, and just cruised, enjoying the enveloping fog with the two 4-legged boys at an easy trot just ahead of me. I almost hated to see the sun coming as the sky over Palomar Mountain to the east began to lighten a bit and the fog began to lift.
I've never liked running in a group of people, having preferred to be a solitary runner, except for the "boys". This really cemented that feeling. Not everyone would like the experience, but if you can, you should give it a try.