>>26393710*f and below = draft proof mummy bag
20* = down quilt xl width
40*ish = down quilt or heavy wool blanket
50*+ = light wool blanket
75+ = nothing
wool blankets are very nice when its hot, maybe the best. down in a nylon shell isn't so nice to sleep in when its hot. wool can't compete on any other metric that matters to hikers such as size/packability, warmth, or weight but it has this subjective thing going for it that makes it a great piece of gear to have. generally you bring less gear for summer weather so the extra bulk isn't such a big deal either.
in serious weather you want to be full fuck enclosed in the most & highest quality down you can afford.
for in between weather, a high end down quilt is the size of a football (slightly bigger for the cheaper ones) and you can open it up for a breeze when needed to regulate your temp.
