Horizon had a lot of trouble maintaining operations during the previous cold snap in January last year when Fairbanks hit -40F. (Delta also had issues.) Part of it was, I think, some people forgot (or never knew) how to keep planes flying in those ground conditions which have been relatively rare the last several years. Another part is perhaps the Q400s are difficult to keep flying in those conditions using only a separate small maintenance facility (the remote part, as in remote from Horizon main ops) designed for only two or three aircraft servicing Alaska, as opposed to the 737 fleets.