Is the Jackson Glacier Jacket actually waterproof?

Yes. The shell is waterproof and windproof, so it handles snow and rain better than a plain down jacket. Seams and long soaking still matter, so it is not a substitute for a hardshell in a storm.

How warm is it compared with a parka?

It uses 700-fill recycled down, which is warm for its weight but lighter than a long parka. It suits typical winter commuting; for extreme cold, size up for layering or pick a heavier parka.

Does it run true to size?

The cut is casual and roomy, so most buyers take their usual size. If you want a trimmer look or plan only light layers, consider sizing down.

Can I wear it for skiing or hiking?

It works for low-output winter activities and resort wear. For sweaty climbing or wet alpine days, Patagonia's technical shells and belay jackets are the better match.