Not -30C, but something similar to this[1] jacket on top of a shirt and warm undershirt have kept me reasonably warm in -20C canadian winters. The best way to stay warm is to have a windproof outer layer, then layer up (light layers!) underneath to trap the warm air close to you.

[1]: https://www.columbia.com/p/mens-centerport-ii-jacket---tall-...

That looks like a pretty light jacket. I might wear that kind of thing skiing, but I'd want something heavier for in-town. A heavier jacket is nice because it's a pain to put on and take off a lot of layers just for a short trip outside.

I have a jacket similar to this one [1], and I find it to be a nice medium. However, if I had to do any work outside, I would get an actual parka.

[1]: https://www.hellyhansen.com/en_ca/barents-bomber-53489

That's the kicker, it's lighter weight, but the "omni-heat" insulation* keeps me just as warm as a heavier down jacket, if not warmer. I even managed to work up a bit of a sweat while outdoors at 3am this past Feburary in my jacket.

Though I don't doubt that I'd need a heavier/longer jacket if I were further north, but here in southern Ontario it's more than good enough.

*Not an ad, just sharing what keeps me warm

The observation about wind proof outer layer is spot on. On the other hand the jacket from the link is too short for my taste. It requires special trousers to match.

One needs something that reaches knees to stay warm in lighter trousers.

That's a fair point, my legs don't really get as cold ime, so that's probably why I glossed over the longer jackets when I bought mine

Just wear lots of layers. They don't have to be fancy. If you are out for a long interval, long underwear helps a lot.