Honestly, it depends heavily on the timing and road conditions. Manali is generally accessible through winter with some caution, but Spiti is a different story the Kunzum Pass and Rohtang are usually snowbound and closed from November to April, making Spiti nearly unreachable by road in peak winter. Even for Manali, roads can get icy and risky after heavy snowfall, so you need a driver who has real experience on those routes, not just someone who has done plains driving. Always check the HRTC road status and Manali local updates before departing. Carry chains for the tyres and confirm your operator has proper hill vehicle insurance. Winter trips are possible but require more planning and the right operator. If you're arranging tempo traveller in Delhi for a winter mountain trip, specifically ask whether their drivers are trained and experienced on snow-covered hill routes.