There are a lot of myths about building in winter. I have heard for years that lumber splits and shatters when you try and nail it when it is frozen the work takes three times as long etc. etc. etc. It is true that lumber with a high moisture content is more prone to splitting than dry wood, it is generally not a problem with good quality graded lumber. Plywood, OSB and metal roofing is not affected by cold at all.
Cold weather has a negative affect on tools which lowers efficiency and profitablility. Saws, nailers, compressors and generators are much harder to keep running in cold weather unless careful measures are taken.
Wearing bulky cold weather gear also slows down progress, but if the work is carefully planned it can be done efficiently. Keeping a large crew motivated is very difficult in cold conditions so a small crew is ideal.
Anyone can work in below zero temperatures but it takes care and planning to work profitably in those conditions. Once you start getting 10 below and colder it becomes more and more problematic depending what you are doing.
I've heard people say that after it gets below zero it all feels the same. These people have never worked at extreme temperatures. There is a big difference from -10 to -30 and even more at -40 and -50.
We have done metal roofing at -50 but it was very slow. The batteries in our drills would only last a few minutes and it was hard to keep our finger warm. It was doable as long as there was no wind but it wasn't profitable at those extreme temperatures.
At zero and above it is very comfortable as long as the wind isn't blowing. Once the wind starts blowing it is very difficult to stay warm even if you can keep the equipment working.
Most winter temperatures in south central Alaska are only extreme for short periods of time so it is fairly easy to keep working throughout the winter.
Reflect upon your present blessings,
of which every man has plenty;
not on your past misfortunes of which all men have some."