State Road 20, California

20 is a good road for rv's. Not flat or straight but like several have said, plenty of places to pull over if needed. I pull my 32 ft. 5th wheel over it and never had an issue.

As others have stated, 20 is fine. Consider 12 to 116 to 101 then on up to Eureka. We recently used 116 to 12 thru your area to Red Bluff in a 37'er towing a car. It was no worse than 20.

Thanks all for the quick responses. Very helpful!

20 is fine -- on weekends, there can be a lot of traffic near the lake. And in Williams, Granzella's has terrific sandwiches -- they make a killer New Orleans muffaletta.

Take Highway 20 West out of Williams. 37.1 miles. Williams is at I5 and Highway 20.

Watch for Highway 53 as you drop down a hill after a fairly long climb. Easy climb and multiple lanes.
Turn what would be South onto 53. You will go about 8 miles. Look for the sign to Highway 29 which leads to Kelseyville. This is a nice road and will become freeway in a few miles. Eventually you are back to two lane for a short distance and will come to a stop sign. You are back to Highway 20 again. This leg is about 30 miles. Turn left and enjoy the beautiful drive right to 101

This route will bypass the two lane twisting and winding on the North side of Clear lake. If you want a good view of the lake go ahead and stay on 20 all the way to 101.

Not sure why you would not take 80 west to 29 Vallejo to 37 to 101 north instead of traveling to Williams over.
I work in Vacaville sometimes and travel this route. Many big rigs, RVers travel this route. Just know there are no rest areas.

To answer your question, Williams to 101 approx 100 miles and just over 2 hours travel. Again, many big rigs, RVers travel this route too. And no rest areas.

Both routes have areas you may safely pull over.

We have taken our 30 ft TT over both several times.

Happy Trails
West Beachhouse

Hwy 20 is a good road---in the past we have taken several different RVs over that route with no issues.

Google maps street view shows it to be pretty nice.