I live in NW Iowa so I feel (literally) the point you make. Technically you are in a disadvantaged position as the bad guy already knows what he plans to do and you have to do more to react in time. As BluesStringer pointed out, physical practice in your cold weather clothing becomes critically important. You also have to develop your intuition (tingling in your spine - spidey sense - whatever you call it). I pay increased attention to minutiae. Like why is that guy checking people out with his eyes more than a casual person walking down the street? Why does that guy have only one hand in his pockets? Why is that woman walking with one hand inside her shoulder bag? That guy has zippers on both pockets, but one is unzipped. It's cold, why is that coat only 3/4ths zipped up? I've looked in the reflection of a window twice now in 20 feet and that same guy is still the same distance behind me, that's not normal.
When you pay attention to what the majority of people do casually as they progress through their day, the small differences that might mean a threat is imminent start to easily stand out. Practice this enough and it will shave time off your reaction speed. It's really not hard to do once you think it through.
“There are no stupid questions, only stupid people.”- Mr. Herbert Garrison
"Never underestimate the power of stupid people in large groups."- Jeff Cooper
"Those convinced against their will are of the same opinion still."- D. Carnegie