Newbie here bought our first prius couple of weeks, i was wondering do i need to warm up the engine? Location San Francisco
Welcome aboard and enjoy the ride! Under freezing, giving the engine a little time to warm up is probably useful.
The hybrid system takes advantage of the battery & motor to ease the burden on the engine. So, there's no need to go out of your way. Even here in Minnesota, I've been just driving away right after starting... for 13 winters now. It's no big deal.
SanFran? Ha ha, no. Try driving in -30 C, then you need to warm it up a bit, only to defrost the windows though so you can safely drive.