Good summer JMT sleeping bag?

You might not have any nights below freezing – then again you might have a few.
I've done the trail a couple of times (July and August) and took a 15 degree down bag. It was warmer than I needed, but I would have been too cold in a 40 degree.

I'd suggest something in the 20-30 degree range.

If the first week of August is still summer… we experienced freezing temps a couple nights and had snow falling on us at one point (between Reds Meadow and Shadow Lake). Not ongoing, accumulating snow, but yeah – snow.

I'd take something rated between 20-30F for comfort's sake.

get the golite ultra 20. Lightweight, good to about 30, and you can air out on days when its too hot.

anything warmer than a 30 deg bag will keep you happy and warm. When my wife and I were out there we shared a warm 2 person sleeping quilt in a 2 person bivy and still needed our insulating jackets and long underwear to keep comfortable. The Golite Ultra 20 with a good down hooded jacket would prob work well.

I did the JMT late August/early Sept this year and used the Montbell Down Hugger #3, a 30 degree bag. For many nights it was OK, I got about 5-6 nights around or below 32 degrees above 10k feet and it wasn't warm enough for me. I had to sleep wearing my fleece. It is an excellent bag but I would suggest a 20 degree bag.

I did the first half of the JMT to VVR with a WM Linelite 40* bag with little problems at all (some times cold). I then change out my bag to a WM Superlite 20* bag for the much higher elevations that you will encounter. You will for sure be sleeping at some very HIGH elevations and Katabatic Air will always be a lurking. It is better to be safe then sorry—When I do the JMT again I will take a 20* bag the entire length.

Goodluck-Jay

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Thank you all for the suggestions! I had a feeling that a 20 degree bag was probably in order… Much better safe than sorry! And the shopping begins ;)

I'd say go with a 30 degree bag, and wear more clothes at night if you need it. A 20 degree bag is overkiil on the JMT in summer – assuming you use your clothes as part of your sleep system. JMO.

Maybe a bag like the Mont-Bell U.L. Super Stretch #2 800 fill? 25 degrees and weighs 1 lb. 12 oz. and sells for $259 right now…

I also looked at a Golite adrenaline… near same specs and price as above…
and the Golite ultra 20… seems more like a quilt that will have to fasten around the sleep pad. Not sure about that. …is light though.

So maybe a 3o degree with polypropylene or silk long underwear for when real cold hits, or just be safe with a 20-25 degree bag AND polypropylene /silk long underwear?

Don't want overkill nor unnecessary weight… but also don't want to be caught with my pants down… in the cold that is.

Get a 30 degree bag that's a couple ounces lighter than a 20 degree bag, and boost it with the MB UL Down Inner Parka (or similar) that you should be carrying anyways for cold nights.

In the Sierra summer months, altitudes 6,0000'-10,5000', I found a combination of a 30 degree bag + Montbell UL Down Inner Parka to be sufficient. That's including a night in the teens and a night in the 20s. (In a tent) I was definitely chilly on the teens night at about 4am, but it didn't keep me awake.

It really is only a few ounces difference between a 20 or 30 degree bag, so it's your choice. I figure I'm carrying the jacket anyways, so why not use it to the fullest.

As far as bags, Marmot and Montbell both make really nice bags that go on sale frequently, but you can't top a Western Mountaineering Megalite or Summerlite (30 degrees) or a Nunatak quilt, they're just pricey.

August 10-24,2009, I used a 20 degree WM Ultralite bag, Big A.Exped mattress and a few nights a homemade bivy, silnylon bottom and Momentum top. Was glad to have this combo for warmth. There was a glaze of ice in the morning on my SMD Wild Oasis shelter along side Guitar Lake. A few nights I slept with the bag mostly open. Just be prepared for the cold. I had hail one PM.
BTW The scenery is beautiful and ever changing.

Great suggestion on the MB UL Down Inner Parka with a 30 degree bag… I figured I would need a light down parka for the chilly nights/mornings. I don't have one as of yet…

I was going to take my MontBell SS #5 (40º) and got nervous so I bought a Western Mountaineering Summerlite (32º) bag for my JMT hike. I thought the warmer bag would be okay because I was also using a MontBell UL Down Inner Jacket. However, I had an e-mail from someone that said they had a few nights at 9,200 ft. that got down to 26º. We had 2 nights where I saw frost on the ground in the morning at approx. 9,000 ft.

Looking back, I was glad I went ahead and got another bag. I never slept with my jacket on but my new bag only weighs 3 oz. more than my 40º bag. Considering all that could happen in the Sierras during the summer, wind, snow, heat, rain, etc. I think a 30º min. bag is prudent. The only problem I see is if you have to spend the first night in Yosemite Valley since a 30º bag is quite warm. We just unzip and use like a quilt.

Wow… the MB UL Spiral Down Hugger #3 weighs in at 1lb. 3 oz. as a 30 degree rating… Seems very comparable to the Western Mountaineering SummerLite, and for $219.

Decisions……..

I happen to have owned both of those bags this summer before settling on a Nunatak quilt. I used the MB 3 times and the WM twice.

The big difference is the interior space of the bag. I'm 5'10", 175lbs with broad-ish shoulders for my size. The Summerlite is a narrow bag and that turns a lot of people off. I was fine in the shoulder region. I could wear a MB Alpine light down jacket in it without compressing the jacket. Where I would've liked more rooms is in the knee region, as I'm a side-sleeper.

The MB bag is plenty wide throughout. I liked it alot and probably would've ended up keeping it over the Summerlite if I hadn't got the quilt.

A couple things about the MB bag though. MB currently sizes their bags differently than everyone else. Regular fits up to 5'10" and the long up to 6'4". This vs 6' and 6'6" with everyone else. So at 5'10", I was told by a knowledgable salesperson I needed a long. That's a lot of extra foot space(and dead air), and it certainly had my feet a bit colder than the Summerlite on similar temperature nights. Not cold, just cooler. I've read MB is standardizing their lengths soon.

Also, the MB doesn't have a full zip. (The Summerlite does) It's a 3/4 or so zip, stopping 26" from the bottom in my long, which complicates quilting it in warmer temps. My feet get warm and I like to be able to poke them out once in awhile.

I never quite hit 30 degrees with either bag. Probably bottomed out at 40 in the Summerlite and I was quilting it to stay cool. In the MB bag it got cold enough to have a little bit of frost in my tent. That night was on snow as well, and I was definitely at the limit of the bag unaided by a jacket. The Summerlite is probably a bit warmer due to the narrower cut (less dead air to heat)

But for the weight, comfort and price, I'd have chosen the MB if not for my Nunatak Arc Specialist.

The WM Megalite is very popular here for 5 oz more than the Summerlite and even more interior room than the MB Spiral Down.

Thank you for that info James!

I am also 5'10" and weigh about 140lb., so I would assume fit into either bag. I am a total back sleeper though, so a narrow cut wouldn't be all that bad in my case… as I wake up just as I go down, on my back in the casket position.

I must admit, you guys do have me curious about quilts… but I am gun-shy seeing as I am so used to a toasty mummy bag…

The biggest benefits of a quilt in my opinion are freedom of movement and being able to vent.
If you don't need the space since you don't move, go with the summerlite. Its continuously baffled so you can adjust where the down is, meaning that if it is too hot you can move the down from the top of the bag to the bottom which will raise the temperature you'll be comfortable at. At least thats my understanding.

I have done it a couple times and am on pieces and in the area a lot. I suggest bringing a 20 F bag for that long a hike as there is no way you can get an accurate forecast for the entire time you will be there. I have seen in drop into the 20s F in August with snow. I have seen it go below freezing in every month of the summer.

A 20 F bag (or 25 like the MB you are looking at) is a good compromise. If it gets too hot, open it up.

That said I used a GoLite Ultra 20 quilt all this summer and just bought a Nunatak Arc Alpinist to use up north this fall. I am hooked on the quilts now.

I have a Mountainsmith Wisp 30 degree and Mountainsmith Vision 15 Degree. These would be comparable to the Marmot Hydrogen and Helium at 24oz and 33oz respectively. I took the 15 degree bag for my JMT trip this year from Aug. 21-Sept. 5. My 30 degree bag has seen a lot of use and lost a little loft and needs a wash.

I experienced below freezing temps near Donahue pass with frost on my shelter. Frost in the meadow at Mclure(Evolution Valley). Also had a frosty night at Guitar lake with my breath frozen on the shell of my bag and the mesh of the shelter near my face. I think I would have been fine with a 30 degree bag and my Montbell Ex. Light down jacket to add warmth instead of just serving as my pillow.

I did have several nights of sweaty feet and legs with the 3/4 zipper and bag draped over my upper body.

Thanks again all for the replies and excellent advice! I admire all of you for having made the trek!

Well, I will probably go with a quality 25-30 degree bag and a MB UL down inner jacket.

Now… I am wondering what pack would be appropriate for this kind of hike. I used to have a Granite Gear Vapor Trail and I did like it… and I am thinking about getting another one for this trip… but I know that I will be carrying a bear canister, and from what I remember of the pack (sold it about a year and a half ago) I am wondering if it is large enough. I will certainly be resupplying, and traveling with my buddy. Is a Vapor Trail enough for this trip? Or should I be looking at the larger(barely) capacity Ozone…

I plan on getting as light as I can… but I do like certain comforts and will be using a tarp tent (GG-the one) and trekking poles (GG-lightrek 4) and a near 1 1/2 lb. sleeping bag (depending on purchase)… so I am not quite ultralight as most of you may be.

The Vapor Trail should be fine for this trip. If you like the pack then use it. There are lighter options but I think the Vapor Trail weights in at 32 oz. Not ultralight but it is lightweight.

Think about what you have in your pack: Tent, ground cloth, sleeping bag, kitchen, some clothes, water and a bear canister. It's not that much stuff. Just make sure the bear canister fits comfortably in the pack. The Vapor Trail has a nice extension collar. It is a nice pack for the JMT in my opinion.

Light weight down bag, gg the one as shelter… sounds like you will have a reasonably compact load. If you are careful in your food selection and don’t bring lots of misc things, the vapor trail should have enough volume for you. I have used a VT with up to 10 days of food + my standard three season kit

–Mark

My WM Megalite is good to its rated 30 F. and I've ben comfortable in it several times (W/poly long johns & balaclava) to the mid 20s F.

It's wide enough to accomodate a vest or jacket and pile pants if the temps drop below the 20s F. "Multiple use" of clothing is the lightest way to go and the Megalite permits this W/O extra clothing compressing the bag's insulation.

The Megalite is wide enough to make a great quilt in warmer weather when unzipped and the foot hooked over the end of a full length mattress. This is the most comfortable way to sleep I've found. To me, with a 42 inch chest. the Megalite is not wide but just right.

Eric