Hi there folks. Looking to ride from San Francisco up to Redding in the summer. Whats the best way to go?? How is the camping on the way up??
Amtrak. Unless you have a lot of time.
If you are serious, there are routes, but they are not easy that time of year. Hwy 101 is beautiful, with lots of camping, but it is a long way to Redding that way because it takes you in a northwesterly direction - away from Redding, which is inland. You will eventually have to cut over on Hwy 36, or 299 or perhaps a smaller route but they are all mountainous up that far north. And the Central valley route parallel to I-5 is hot as blazes in the summer - Chico can be 100 and Redding can easily hit 110-115 since it is at the far end of the Central Valley and gets no coastal breeze. And getting out to the valley is not that easy but I suppose you could go up through Napa and cut over at Clear Lake to Williams. That will be very hot also, though there should be plenty of places to camp.
Bruce Gordon Ti Rock N Road , Fat Chance Mountain Tandem 
If you have the time the Coast Route Hwy 1 is a wonderful ride all the way to Eureka/Arcata where you can join Hwy 299 to Hwy 96 to Yreka and them South by several options to Redding. My preferred route due to prevailing winds on the coast is to travel from Redding to SFO on the above roads. Is reversing the route an option for you? Adaptable camping consisted of hiker/biker sites on the coast to guerrilla camping and forest service and commercial campgrounds.
I have used a rental car,bus or Amtrak to reach Redding or Klamath Falls,Oregon to start tours heading West to the coast or East to Lassen and down to Lake Tahoe to avoid much of the Central Valley and Redding Summer heat. Have a safe trip whatever you chhose to do.
I agree that the valley tends to be very hot during the summer. The temperatures along the coast are much cooler. The wind is fairly consistently a headwind if you head north; however, it usually kicks up in the afternoon. If you were to ride extra early in the day, and camp early, you could avoid most of it.
If you really want to ride in the valley, my suggestion is to take the ferry to Vallejo, then ride the backroads and bike paths to Fairfield and Vacaville, and then head north and northeast, following small backroads as much as possible.