The Shimano downtube shifters are light-action shifters. IOW, you don't need to make them too tight. If you insist, you could move to bar-end shifters, but I don,t think I would recommend STI for serious winter riding and/or outside parking. I have no direct experience with it, but I'm afraid of what the innards would look like when shifting at -30 C or on a day with lots of icing rain.