Originally Posted by
ooga-booga
coastal california is your best bet. higher humidity but at least 10 degrees warmer at night. if you do tackle inland and low-lying california (4+ miles from the coast) dec-feb, you will be looking at low 30's fahrenheit nightly.
high/low temp swings along the coast will be 20-25 degrees vs 35-40 degrees inland/desert dec-feb.
but if you're sold on the vegas start and wanting to head into california, i'd research hitting death valley national park. dunno your fitness...dvnp ain't the easiest place to climb out of...
hence the name. super scenic tho and the stars are phenomenal.
I agree with this, about being on the coast. The proximity to the ocean is a powerful buffer against temperature swings. It can only get so cold. No way it'll get into the twenties. The problem with the coast that time of year is the rain. Four weeks is a long stretch to hope for no Pacific storms, which are unrideable. It is the rainy season, after all.
If it were me, I'd stay flexible and try to finalize it at the last minute, once you know the long range forecast. You could get lucky; San Francisco didn't have any rain last February. First time ever.
San Luis Obispo would be a good place to start. Morro Bay is just a little bit North, Big Sur a bit further. SLO has tons of amenities, so you could spend a few days in comfort if you need to let a storm pass. Amtrak gets you there from both ways, weather you fly to SF or LA. You easily could ride from there, down the coast then take the Southern Tier to Phoenix with the amount of time you have. That's if you get lucky with rain. It's been a dry rain year so far, though.