I will be breaking this blog into three sections; rain, snow, and sun. It's pretty self explanatory as to what I will be discussing in each category, so lets begin with the second one, Snow.
I find that a base layer is not always needed. Only in the coldest days or extreme environments, should you need one. However, I have found that a base layer is great to wear underneath your regular pants on chilly mild days.
Choosing a base layer is fairly simply, you have bottoms and a top. They come various styles and a few different fabric choices. Base layers are not that thick, so I would suggest the thickest pair of 100% Merino Wool fabric to keep you warm. Merino Wool is ideal for regulating a steady body temperature in both cold and warm environments. And then add on a Merino Wool long sleeve top and you're set.
The best mid-layer is a thick Fleece sweater.
Any kind of a high fill down jacket is ideal as an outer layer. I would recommend anything made by Arc'teryx or Patagonia as these two brands are highly trusted and they are known to source their down in a cruelty-free way (picking up each individual feather from the ground and cleaning it), where other brands may physically pluck feathers directly from the birds.
A shell is not always needed but good to have. I have more information on choosing the proper shell in my other blog here.
A shell jacket in the winter time will protect you from the elements whereas an outer layer may not. The shell will keep you dry if it snows or rains. Additionally, depending on what you are doing, it would also be a good layer of protection from your outer layer.
My favorite gloves come from The Heat Company. They make amazing gloves, both liners and shells that are IDEAL for photography. If you do not need gloves for photography, you can find cheaper alternatives elsewhere, but because I am a photographer, I decided to purchase this specialty pair from northern Europe.
A good toque is highly recommended. The one I have is the Arc'teryx Word Head Toque, made of 50% Merino Wool, which is the best fabric at regulating body temperature and keeping you warm in winter. Ideally, you want something that does not have holes as many are fashion statements and don't keep you as warm as they look.