Rivnuts from Homestead,PA on 8/18/2023 9:06:00 PM:
As you know, there is no car/motorized vehicle traffic on these trails other than a few blocks exiting Pittsburgh and leavin McKeesport. There will be a fair amount of walkers and cyclists near Pittsburg and DC but not to the extent of presenting any danger or delay in your progress.
It’s too early to make a believable forecast of the weather for that weekend. But, for what it’s worth, the current long range forecast for Pittsburgh for Friday 9/1 is for partly cloudy skies with a daily high of 77 and a nighttime low of 58F. You can check those daily forecasts as you get closure to that time.