It's certainly doable, especially with a support vehicle to carry extra water, but you may see some uncomfortably hot weather. From San Francisco, you'll be fine for the first day or so until you reach the Central Valley around Davis and Sacramento. While briefly in the Central Valley, temperatures can easily soar well above 100 along with moderate humidity. The weather should become much more comfortable as you climb into and over the Sierras. Expect the hot weather to return with a vengence as you enter Nevada, but this time with very low humidity. Consider planning long rest breaks during the middle of the day to avoid the worst of the heat. I'd also suggest looking into atypical cycling clothes, such as light, loose-fitting jerserys.
This weather should stay with you all the way across Nevada, but will likely become a little milder as you enter Utah. In Utah and Colorado, the weather will be very dependent on the altitude: hotter at lower elevations and cooler at higher elevations.