The morning grey had given way, in the sudden English fashion, to a brilliant, gelid afternoon.
Zoë Heller, Notes on a scandal

Gelid, adjective
Very cold; icy.
From Latin gelidus, icy cold, from gel(um), frost, cold.
I love being surprised by an unusual word when reading a novel. I had never come across "gelid" and it delighted me, maybe because it is one of these words that start off in a very familiar fashion (a host of French words coming from gelum gel, gelé, gelée, geler, gelure, etc.) but ends rather less predictably. Somehow I find it so much more evocative than "freezing", "bitter" or "icy", but that’s probably only because these are so much more widely used and, frankly, leave me a little cold.