Layer question for early Sept JMT — is fleece enough or do I need to go puffy?

It depends on you, but September is when the temperature starts to change, and when it happens, often transiently it is true, the average temps can drop 20 or more degrees overnight. Plan for the possibility of night time temps down to the low 20's at the higher elevations. If you aren't also bringing a 20 deg bag I would say you may be in for some discomfort. Personally I'd never go to the high sierra without a puffy layer, even in mid summer.

If going to be camping above treeline I would take a Puffy + good sleeping bag at least 10degree warmer than coldest expected temp. Unless you are a very warm sleeper.

**Edit**

It's a slow afternoon, so I've been reading through lots of the threads on down jackets I've skipped over in the past. Looking at the Mont Bell Alpine Light jacket with 4oz fill at this point. Also seems lots of people say that for true shoulder season temps the U.L. can fall short when sitting around in camp. But in pictures the Alpline Light looks like overkill, and the U.L. seems more in line. Not sure now.

Again I've learned there is an impressive archive of threads on this site once you switch to Google for searching. :)

I was planning on my 20 deg RevX quilt. I was going to take my zlite pad, but am thinking I might need more insulation that that? My trip was originally planned for early Aug but some scheduling issues with family members pushed it back, into more marginal weather for my gear.

I guess I should have also asked, is there a rule of thumb for how heavy of a puffy layer I'd need (nano-puff v. ul down jacket v. X?). I've heard decent things about the Uniqlo down jacket recently.

Since a light puffy is half the weight of a fleece, Im not sure where the dilema lies.

Once summer I spent June-August in the Sierra and there wasn't a single week where I wasn't glad I had my Alpine Light. Lighter, smaller, and way warmer than fleece. If I did it again, I would take the UL Down though. For September, the Alpine Light is perfect!

Puffy. I haven't used fleece in the mountains since the mid 80s. I find that most alternatives outperform fleece. Puffy for insulation at lunch, belays (climbing) and in camp. Softshell for wearing on the move in the cold. Fleece is for in town (if at all)

YMMV

Obviously the fleece is smarter for wet weather, and the puffy down is smarter for dry weather.

September along the JMT is unpredicatable. Sometimes there is a continuation of the dry summer season, only getting cooler. Sometimes the autumn weather arrives early, so it gets wet and nasty. A last minute decision may be called for.

One year a young couple was camped just below Mount Whitney over Labor Day Weekend, and they got rained on. Their gear was getting wet, and they didn't know when to cut and run. They waited until the snow was piling up before they descended, and their bodies were found the next day.

–B.G.–

+1 for Bob's assessment of the weather in September.

Have you considered a synthetic puffy?

-Peter

How cold have comfortably taken your current layer system?
What about adding a light puffy and keep the fleece as well?
For only $50 and only 9oz. the Uniqlo parka might be enough when added to your current system without breaking the bank or your pack weight.

I just ordered one, and it will be my first down puffy. When I tried it on at the store I was very impressed, but I don't exactly have anything to compare it to other than my current primaloft puffy.

Jim,

I've used less than you on the JMT in early Sept but I went to sleep as soon as I stopped.
There was no sitting around in the cold for an hour or more.

The only way I could see this work for you is if you had something like a Nunitak wearable bag.
I would get a down jacket. You will be cold.

Although it worked for me, the only thing I would have changed with my trip was to take that down jacket.
At the time, I didn't have anything between a MB Extra-light and 19 ounce down jacket.
I had too many layers to have the Extra-light on top and I wouldn't have had any need to wear it during the day.
It's supposed to compliment your sleep system and add degrees of warmth. The Ex-light just doesn't help more than a few degrees.

I hiked the jmt last September. I also brought a 20 degree revx and, combined with my feathered friends daybreak jacket I was comfortable the 12 nights spent on the trail. It indeed gets cold there at night especially the last half whee you are camping higher and higher in elevation. I concur with the other threads in saying you should definitely bring a puffy. Side note: my hiking partner brought an ex lite and he wished he had a little mor insulation.

Thank you all for the responses. I'm definitely planning for colder temps now. I actually ended up stumbling into a deal on a Mont Bell Ultralight Down Parka (2.5 oz fill in jacket plus a hood). I probably would have ended up with something with a bit more fill, but the price was too good. I will likely plan on bringing bring the fleece as well, unless the weather forecast is leaning way in the other direction.

Side question to those who have a bit of experience up along the JMT. What is my best method of tracking the bug situation? I imagine it's tied to water levels? I'd like to just use my flat tarp and carry a headnet for insurance, rather than a fully bug bivy. If the weather forecast ends up iffy or calling for rain and cooler weather, I may add a bivy anyhow, making this question moot, but advice is still greatly appreciated.

"What is my best method of tracking the bug situation?"

Check out the High Sierra Topix Forums, specifically the mosquito reports thread in the "Conditions reports and information" sub-section of the "Backpacking/Hiking/Camping" Section closer to the date.

In general September in the Sierra is past the end of Mosquito Season, especially in a relatively dry year as this has been so far.

Dave

As a general rule the mosquitoes are gone to the point of not being an issue by August. By September that will be long gone.

this type of question is asked here so often its like a broken record.
why do so many people insist on going into the Sierra on the edge of unprepared ?
we're talking ounces here, maybe even a whole one pound.

I agree with Art. Besides, some of us need a puffy while sitting around with someone wearing a Tshirt. You could get as many answers as there are BPL members. Nothing wrong with asking the question, but giving the correct answer for your needs is nearly impossible, short of recommending that you be safe and bring enough warm clothing.

Yes! Was tempted to say if he hasn't tried it himself there is no way of knowing for sure. It like asking people if a particular model of shoe "fits". As for me I'm going to a full on Mirage in September. The extra 4 oz of weight is a low weight luxury for a cold sleeper.

Well my question was answered, so thanks to those who responded.

Anyhow, my purpose of asking here was to get opinions/experiences. Never having been up in the Sierras at that time of year, I was concurrently checking weather history, trips reports, etc. I suppose I could have waited till I'd done more research myself, but I would have ended up answering my own questions and not having an excuse to engage the boards here.

It seems that in general people on BPL don't mind repetition too much, often happy to give a response, rather than typical internet forum speak like "read the faq" or "use the search." But if the preferred etiquette is to not ask a question until you've exhausted other options, I won't rock the boat in the future.

Another tendency on here amongst some, in addition to not minding repetition – beating up on straw men.

You definitely have to start somewhere (catch-22), and your choice was an excellent one! Have a great time.

I just meant that there are great differences among us when it comes to how much insulation we need.
I ask plenty of questions that have been asked ad nauseum.

Edited . Autocorrect does not like Latin..

When I did the trip in early September, I took a down sweater. This, along with light Icebreaker base layers was not enough. We got snowed on the second day.

We had friends bringing our resupply and joining us for the final stretch at Dollar Lake. While at Muir Trail Ranch we let them know to bring our heavy Icebreaker hoodies. It's tough to know right now what the weather will be like, but I'd definitely have a heavier puffy on backup next time. I was mostly cold in the evenings and at night. Mornings were also cold, but that quickly changed once we got moving. We rarely started hiking with the down sweaters, but they were on all evening and all night most nights. This was with WM Aspen 25 degree bags, Neo Air Large pads with GG Thinlight pads underneath, and a Lunar Duo.