Fellow PBP-heads -
I have checked this site a couple of times and it has convenient links to local weather conditions and longer range forecasts for several control towns on PBP.
While the weather will certainly change between now and the time we ride, in about one week the forecast will include the 21-25th. The forecast can help riders decide what to start the ride with, versus what to put in a drop bag.
I think a temperature range of 50 to 75 degrees F, with at least some rain during the ride days would be a good guess based on what I've seen. If temps get lower than 50F near Brest, it's possible we could also see fog. But to contrast, another rando's site was suggesting that it could be a hot spell during the ride. Pick your "science!"
Bob