LL Bean catalogue a few days ago and saw packable warm coats for temps between 35ºF and -20ºF.
LL Bean's stuff is generally a pretty good value buy. Not the best, but a very good value. Now that said, just be aware of Bean's temperature comfort rating. Bean explains the rating as follows: http://www.llbean.com/llb/videos/512476?type=V&channelId=512396&autoplay=Y
The first number of our comfort ranges is based on a computer model
simulating a person engaged in light activity, such as walking. The
second number is based on a model simulating a person engaged in
moderate activity, such as running or skiing. Because an active person
generates more body heat, the same piece of outerwear will be
comfortable at a lower temperature.
Here we determine the temperature ratings for outdoor apparel. First,
the mannequin is dressed in the L.L.Bean base ensemble. This consists
of thermal underwear, a fleece shirt and jeans, a knit ski cap,
mittens and boots. Then we add the jacket to be tested.
First note that the jacket's temperature rating is not based on standing around doing nothing (e.g. waiting for a bus). The first, higher number, is the still air temperature of a person walking. The second, lower temperature, is active exercise.
Second note that the jacket is tested with an appropriate base layers. For the Bean rating, the base includes a thermal base layer and fleece shirt in addition to knit ski cap, mittens and boots.
If you watch film clips of cross country ski racers, they race in un-insulated Lycra ski suits over a wicking base layer. Yes they do ski with ski caps and gloves, but no insulating layer at temperatures as low as -25C.