Matt,
Good for you for venturing out on your Raven in such conditions! Now I understand why my grandfather, one R Burns by name, left Aberdeenshire for London, a century or so ago...
My B17 doesn't have to endure the same weather as yours--I tuck my bike into the basement workshop for most of the December-to-March period. There's a lot of Hard-Man mythology about Canajans--much of it self-glorifying, you may be sure--but we're now a very urbanized society, and I'd guess that the majority try to avoid weather like yours. So, good on ya!
What do you rub into it?
My LBS was out of stock on Proofide when I bought my saddle a couple of years ago, so I simply substituted Obenauf's Leather Treatment which I had on hand, sometimes in the "Leather Oil" form, sometimes the "HD" paste. Obenauf's is a firm in the US Pacific northwest. Have found their stuff to be exceptionally good--I learned about it on a hiking site, and use it on all my leather boots & shoes, jackets, and saddles.
Press on regardless, eh?
J.