Are you doing the TT? It has been pretty darn warm here lately with temps near 100 in northern SoCo. That section from Lake Sonoma on Skaggs Springs should be toasty. Although they are saying high of only 80 so maybe you will luck out. I rode that section two weeks ago and the fog was so thick we finally turned around since you couldn’t see very well.
There has also been a lot of road work on Gysers Rd due to winter damage from two years ago. You may hit some gravel sections and of course River Rd from Calpine facility down to Cloverdale is always a mess. Good luck!
It was in the morning so I am sure you will be fine by the time you reach that point. I was just pointing out how the temps can really vary as you get closer to the coast. I doubt you will need arm warmers much past Santa Rosa. Seems like forever since we have seen fog around here which is pretty strange for June.
Planning on riding the course on Saturday too. Coming from SF, I usually start at Windsor High Schoool. It’s a 60mile loop that hits all but the initial 3-5 miles of the course. I plan on rolling around 8/8:15 from WHS if interested.