Just talked to one of the ME's at Vertex today regarding their solar system. They had done some testing in the field in cold climate. Here's what he said:

Operating Temp

a. We have ran the compressor at 0* F for an extended period of time in a freezer down here and haven’t had any issues.

b. The Compressor that is in Ohio got to temperatures as low as -29 (F) middle of night not running, and coldest max temp of 1 (F) during the day. (Chardon, Ohio)

c. The Electrical components are “Industrial Grade” (-40 to 212 F

I've run a Thomas diaphragm compressor (albet a "grid" system that ran 24/7) that was in a very open enclosure. No way would the temp in the enclosure rise even a degree due to compressor temp, but since the compressor never shut off it isn't an "apples to apples" comparison. But, the compressor has seen temps in the low teens (below zero) and it lasted 10 years before needing to be rebuilt.
3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).