I hike in the Canadian Rockies. Here it can snow anytime of the year and can often dip below 0C (30F) at night.
I plan to bring for tops:
Either a long sleeve nylon shirt (6oz) or both a short sleeve and long sleeve nylon shirt (12oz)
A midweight fleece shirt (9oz)
And rain shell (12oz) or if it plans to be nasty a lot of the time, a goretex parka (35 oz) ya, I know it's a whopper! Mil-spec tho.
For bottoms:
Nylon wind pants (10oz)
Midweight fleece pants (11oz)
And if it is really cold and suspecting lots of rain I'll bring goretex pants (19oz) They are mil-spec also and VERY warm.

When I was workin oil patch I'd wear a t-shirt, hoodie, rain jacket, polyester work pants, Gore-tex pants and then covies over everything. I was warm down to -15C (5F) and you stand around outside not doin anything a lot of the time.