JMT….. leave the down jacket at home?

It depends entirely on what else you are taking.

Last year for an early September JMT through-hike I used a merino SS T-shirt, a 100 wt fleece pullover and a MontBell down inner vest. I also wore a lightweight LS button-front shirt mostly for sun protection. I also had a 200 wt fleece watch cap and mittens of the same stuff. I had a pullover wind-shirt available to cover the layers. For the bottom I had lightweight nylon cargo pants and a pair of Capilene2 long johns.

I saw temperatures as low as 26°F in the mornings. A few times I would drape my sleeping bag around me to add to the insulation. Overall, I stayed pretty comfortable. I don't think I would change much if I were going again soon.

thanks rincon for your help! Likely will leave it home being that it is mid summer and minimal evening camp time. Plus there is the down sleeping bag to wrap up in too.

I bring an ultralight down inner jacket (montbell) with me in the sierras in and around the JMT, and wouldn't leave it at home even in summer. It can get <40F many nights at altitude even in the middle of summer once the sun goes down. A heavy down jacket would be overkill.

But you would be fine wearing your sleeping bag if you really didn't want the extra weight…

I almost always carry a down sweater with me in the Sierra. Two weeks ago I left it as we were pretty sure that we would see nothing lower than 42 F where we were going, south of the JMT. Of course the first night got down to 30 F by 1:00 am and stayed there until 6:00 am.

I have done the JMT two years in fall and had to carry a lot of warm gear, but I have seen many summer trips that the temps drop below freezing up there. I would suggest bringing it. It makes a great pillow if nothing else.

The down jacket in question is a MH phantom, 15oz.
My sleeping bag is a MB UL SS #2/25F 1 lb 12oz.
Does that change your perspective?

Cheers

If I was planning on any significant down time I would bring the down jacket. They are just so comfy.

Another recommendation to bring the down jacket – I was in the San Jacintos this week, well south of the Sierras, and a chilly wind at sunset had me snuggling in my down jacket!

The down jacket in question is a MH phantom, 15oz.
My sleeping bag is a MB UL SS #2/25F 1 lb 12oz.
Does that change your perspective?

Not a bit as that is my down piece of choice too. It has well over a thousand miles more on it since I wrote this:

http://www.backpackgeartest.org/reviews/Clothing/Jackets/Mountain%20Hardwear%20Phantom%20Jacket/Owner%20Review%20by%20Ray%20Estrella/

I guess I should update the review for BPL, huh?

I have been in the Sierra when it dropped into the teens. We saw it go two days without breaking 35 F in September. One time Dave and I went over Island Pass and took our shirts off because it was a balmy 40 F for the first time in three days. That was on October 1st or 2nd.

But I can't remember all f the times that I have been in the Sierra or the Whites that it dropped below freezing in the summer. The TR I wrote for Backpacker Magazine of our first climb of White Mountain was hilarious because of the weather. We talked to people in shock from the snow and hail, along with the wind and sub-freezing temps. In August. And the week before I was sweating my butt off directly across the valley on a climb of Middle Palisade. So I told Dave, we don't need warm stuff…

But by all means, use your own judgement. That is how good TRs are born… (Heck the epic ones get book deals.)

Having just got off the trail last week, I would say take the jacket with. The temps dropped quite a bit at night, and unless it warms up significantly in the next couple weeks I can't see getting by without something warm.

I have hiked for 10 years in July/Aug in the High Sierras, mostly the High Sierra Trail but last year the JMT and again this year, the JMT. I always bring a ultralight down jacket and have always used it. My sleeping bag is 1 lb 3oz Summerlite by WM good for 32 F. I handle colder nights using the down jacket. I'd rather split the weight this way than put all the eggs in the bag. The last night when you hike up Whitney starting at 3:30am (a very common time for the last day), it can be quite cold. I would not want to hike up Whitney wrapped in my sleeping bag.