We don't get temperatures like that here in the UK very often, but I would expect it does effect line characteristics over a long distance.

Here it was once a common thing that SnR values would fluctuate even in heavy rain, but there has been significant investment in sealing up the network to try and prevent that, and certainly towards the end of my time at BT had gone a long way to reducing HR Disconnection and poor SnR faults. You only need one bad crimp on a run to have a massive effect, weakest link in the chain and all that.

It would be interesting to see a graph of line performance against outside temperature

Cheers

Cris.