Which bag?

[maverick]

A 20 degree bag is the best option for the high Sierra from late spring to early fall.
You have the option of taking the 45 degree bag, a fleece or down jacket, a warm hat,
warmer underwear, which will all increase your pack weight.
With the 0 degree bag just unzip it and use it as a blanket, and if it get cooler
during the night just zip it up.

[AlmostThere]

I always take a 20 degree down quilt for three season Sierra hiking. Less bulk, plenty of warmth. Have been comfy between 50F - 20F with it, and easy to tuck in or open out as necessary. (I am a cold sleeper.)