I was up in the Old growth Sequoia forests just a couple of weeks ago (mid December). We went to General Grant, which is on Google maps for directions. General Sherman was not accessible from the south side roads due to snow. Make sure you have chains for your vehicle's tires, as they require at least having them in the vehicle during this time of year in the mountains there. We camped in a tent, down near Bass Lake the day before. They have rental cabins/houses at the pines resort nearby. It gets COLD in a tent, but we survived! If you want to go to see the beautiful old growth Redwoods, I recommend "Jedediah Smith Nation Park & campgrounds." We tent camped there & it is absolutely amazing! Bunch of trails nearby and along a gorgeous river! Enjoy!
My wife and I have only been to the Redwoods near Crescent City in September. Beautiful and not that cold. I can't help with any information about January.
Redwood forest is different than sequoia forest. Are you going to the redwood forest near crescent city or are you going to the one near Bakersfield? The one near crescent city can get really cold in January. Temperatures can drop to freezing temperatures at night.
Well you'll definitely want to camp out in a cabin not in a tent January is wrong time of year to be camping in a tent in the forest you need to rent a cabin
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