Yosemite bag temp for August 20f or 30f?

Either one is fine. If you are a normal (not cold or warm) sleeper, you might be chilly 1 or 2 nights out of 10 with a 30F bag but you'll save some weight. With a 20F bag you're pretty much guaranteed to be warm but the bag is heavier. Depends where your priorities are.

For what it's worth I use a 20F quilt 99% of the time but often I sleep with it pushed down at my waist or with a leg outside until it gets colder early in the morning during July and August.

If u r spending the nights on the valley floor, 30 should be plenty fine

Aug 1 or Aug 30?

6500 ft elev. or 11,000 ft elev. ?

In the valley, you will likely sweat with anything lower than a 40F-50F rated.

Yosemite ranges from 2000 ft to 13000 ft elev.

In the Yosemite high country, you can get snow in just about any month of the year. In the summer, it tends not to snow very much, and it melts off quickly. However, you have been warned. Also, it depends somewhat on whether you are sleeping in a tent or outside of a tent.

–B.G.–

For what it's worth:

This past summer on the JMT (August 20-September 20) I used a Katabatic Palisade (30*) and was perfectly warm the entire trip. I brought a Rab Xenon as a warm layer and only had to wear it to bed 2-3 nights towards the end of the trip. For the rest of the trip I wore REI midweight polartec leggings and a cheap polyester thermal to bed. I generally sleep pretty damn warm.

Think about your layers to in relation to which degree bag you want to use – if you're going to bring a down jacket or similar, sleep leggings and socks, I suspect you'll be fine with a 30*.

Dylan:

To add to the complexity of the topic at hand, a Palisade has the same stated loft as a 20F Zpacks bag.

Thanks for great input. It is somewhere in August 12-20 and starting at Tuolmne Meadows, topping out at 10,000 one night then working down to the valley.

You haven't said how you sleep, cold/average/warm. This is crucial. Posters saying what temp bag they use should state how they sleep as well. They may have been fine with a 30 bag, but if they sleep warm and you sleep cold you won't be comfortable.

Good point.

I sleep average to cold.

Plus I expect to be wearing some kind of long sleeve tops and bottoms like Cap 1 and socks.

At 10k feet in August, I think a 30 degree bag would be adequate even for a cold sleeper. The long underwear probably wouldn't be necessary for that trip. Also, I find that long underwear don't provide a lot of warmth for the weight. A few extra ounces of down (effectively going from a 30 degree to a 20 degree quilt) are a much better utilization of weight for a sleep system.

I can only afford one quilt, so I've found a 20 degree is pretty versatile for 3 seasons in the high Sierra, from 10k to 13k.

No wonder I was so damn warm.