The biggest drop in range in the winter by FAR is heating the cabin. All the other losses are insignificant in comparison.
There are two schools of thought:
1) You'll get 60 miles of range when the weather drops below 45. This assumes you want to heat the cabin, even a little.
2) You'll get the full 70 or more miles of range, but you'll use the seat heaters and blankets to stay warm. (You'll also preheat the car before you leave).
One more caveat, if you drive around 45MPH, you'll do much better than 60 in the winter.
Have to disagree a bit. Even without cabin heating you are not going to get 70 or more miles of range in subfreezing temps. I regularly drive to a town 70 miles away on country roads, averaging 40mph, flat the whole way. In summer I arrive with >10% left; in winter I have to charge along the way even if I try to tough it out without cabin heating.
In my experience freezing weather leads to a usable capacity of under 17 kWh so even if getting 250Wh/mi or 4mi/kWh (nice weather numbers correlating to 60mph), you can go 68 miles at best. For various reasons you won't actually see 250wh/mi in the middle of winter, at least not at highway speeds, before you even consider cabin heating. You could probably make it 63 miles if it isn't snowing, but it would be very very close.
And going without cabin heating is sometimes easier said than done. Jamie can manage to go without heated air because his commute takes 20 minutes. Drive 45mph for 30 miles and you are in your car for 40 minutes. Frost on windshield will develop, nose will be numb, and even if you trudge through it, why would you choose to suffer just to make it barely work?
To the original poster- If you have a second car for those admittedly few days that winter throws its worst at you, you will love your quiet smooth FFE ride during the other 3 seasons. But if you have to fret over each minute you run the heater, drive in ski gear to keep from shivering, choose between driving slower than everyone else on the highway or using surface roads that are sure to be last to be plowed, etc, you will not love this car.
Last thought- any public charging options on the route? 30 minutes at a level 2 charger will get you 3 kWh, adding 10 miles range or so and giving enough of a cushion to reliably make it with modest heater use. Adding 30 minutes to a commute home might not be so bad depending on how often you'd have to do it. I wouldn't count this option valid unless there are several charging options... I've seen enough public chargers break, get abandoned or otherwise disappear to not count on any particular one.