Plainly put: cycling in snow and rain and -10° C is not a big deal, once you are used to it. The trick is to start in summer, do it every day and just never stop for any weather, e.g. for your work or uni commute.

Obviously you need something that protects you from occasional rain or at least some dry and clean clothes to change into, but apart from that, the seasonal change will not be harsh. It is usually gradual, and yes, you will at some point want to wear gloves, and long pants, at some point even long underwear (or specific biking clothes), but it is never suddenly cold. Actually you become less sensitive to the cold overall. At least that was my experience.

To be fair, I stopped doing that a few years ago, since not having a shower at work makes slightly longer commutes uncomfortable with co-workers and clients, obviously. And I became more and more afraid of my laptop in my backpack, because yes, you will get wet, your stuff will get wet, you will slip on snow, etc.