Last winter I was vectored to an ILS at the same assigned final altitude prior to intercepting the glide slope that they use during the summer
It is quite possible, as I said above, that the assigned altitude was quite OK and had been chosen to take account of the worst case but who knows if it is not mentioned by ATC at the time or written down somewhere. It would interesting to contact the ATC manager there and ask the question directly, the airport has a website and it should be simple enough to get a contact number for the tower. By my tables you would need to add 970ft to a 4000ft platform at -40 which is a huge error if not being corrected. -20 is about as cold as I have to deal with but it's still enough to need a 90ft correction to a 600ft MDA.
Roll on summer!.