Anyone heard of a IL/AL facility executed a fire drill during the dinner hour, in the cold and dark?

Yes, unfortunately pamstegma is right. Law requires we do some drills at night, at dinner, even while they'd be sleeping. One-size-for-all over-regulation is often not done with any logic in mind. Of course it's needed for safety and some people never do the drills.

I've been to my Dad's Independent Living building when the fire alarms went off, and everyone had to head to the main front door and go outside.  One time it was pretty windy.    It was a false alarm.    Apparently someone burnt some toast in their apartment.   The fire trucks did come, so to my Dad it was worth the long walk down the hall and out into the chilly weather.

My sister's group home does a night time drill. I think this is required.

Sometimes the timing of a firedrill comes from corporate and there isn't a lot of advanced notice. So that they will react just as if there'd been a fire. They should have let you gather in common rooms or somewhere else indoors out of the cold. They could have had a late dinner day. Seems like it would have already been prepared.

My elementary school used to have fire drills and not allow the kids to put on their coats - used to make my grandmother bananas. Fire drills are important for safety, if they interrupt dinner they need to make arrangements to get people fed. Complain - I do agree 45 of awfully cold to send a bunch of elders into.