I have jackets for my two (Kelpies). A thin waterproof which gets used when walking in the pouring rain to save having to dry them both off (especially on a morning winter walk as they live outside during the day in kennels and i wouldn’t want to put them into the kennels while wet).
And a thick insulated one which they get in the kennels if the weather is going to stay below freezing for the day.
I rarely use either when we are out on the hills, again unless it is subzero, as they are so active, but I do take them in the car (winter evenings) so that if the wet dogs are left in the boot while we go to the pub on the way home they are okay.
The waterproof ones are cheap and cheerful, but are wearing / washing well HERE
The insulated ones are more expensive with two velcro belly straps and leg loops as they need to stay in place all day HERE. I am particularly impressed with the way these are made and fit. They are better than the web page looks!
I also have the harnesses which (i think) surfer means above with a handle to help them over gates. There is also a rope attachment point for if the scrambles get a bit steep and you need to give them a hand up. I think they are ruffwear and they give a good coverage for wind / wet protection.
Whichever you use, just check for strap rubs when you are out on a walk. All dogs are different shapes and what works for one may not work for another.