by any sensible definition of northern california, yes, easily and obviously, since it includes the bay area. if you are only talking about the state of jefferson area in the far north then he would probably lose but idk there are still lots of libs in those parts
biden won both humboldt county and mendocino county pretty handily in 2020 and i would bet real money he will win them again this year. my guess is that the real heart of reaction in norcal is in ranching and ag, just like elsewhere in the west