I have the ~100 year old shed part of a ~160 year old barn over it. Boy was THAT a lot of work .... for someone else!
No problem in cold, still works fine at -20F. I can see where freezing rain could glue it shut or a dump of snow could keep it from opening since it opens out. Of course freezing rain could keep any unprotected chicken door from opening. I think I would build a little 3 sided roofed "porch" in front of the chicken door (auto or not) if my coop were not in the barn. Or, if it opens to a run, cover several feet of the run where the door comes out.
I would get the photo sensor if it is safe for your chickens to be out of the coop on their own during daylight hours. Otherwise you will end up having to reprogram the door as the number of hours of light changes through the year. It is only $15 and there would be no extra shipping cost if you get it at the same time as the door. I didn't do that and wish I had. Got it last year and it works great.