WM Summer light – How Cold?

My experience leading groups into the woods all winter for two winters is that everyone is alarmingly different. Different metabolisms, different amount of food eaten that night, different comfort levels, etc. Survival is probably similar, but comfort is not.

I, myself, figure out my range as the temperatures drop on my porch. I slowly reduce the amount of insulation relative to the temperature until I cannot sleep. Once I know where that point is, I spend the next 5 months choosing my sleeping bag and insulation confidently.

I would look at what you already have, and assume the WM bag is going to be exactly what it says it is. If your 30º bag is comfortable at 30º for you, a WM Summerlite will definitely be comfortable. And keep in mind that your fluctuation could be due to something as simple as whether or not you had food before bed.

Personally? I took a 20º bag and a 45º bag together down to -15ºF last winter, and I managed to sleep a night at -5º using just the 20º bag. If I owned a Summerlite, I would probably take it to 10º.

I also took a 45º Quest bag from the 1990's down to 20º… so I'm not a good example. A girl in our camping group made it past my foolproof gear shakeout with a 45º bag for a Maine trip. I had no idea. Since our spare bag got wet, I gave her mine and toughed it out. It was a 5'5" bag and I'm 6'2", and I still managed to sleep through the night in a synthetic puffy and rain gear. We had a big laugh about it in the morning when we actually read the temperature.

I have a Summerlite and I start getting cold in it when the temperature gets to the mid thirties. This is with a 100 weight fleece top and Capiline 2 long johns on. I also had the bag overstuffed with 2 oz of down. It is a good warm weather bag but is marginal for use in the western mountains.. For me the bag is a bit snug for a down jacket to help much because the down in the jacket gets compressed. I am 5' 9" tall and 160 pounds. The Summerlite with the overfill weighs almost 22 oz. My Marmot Helium 15 degree bag weighs 28 oz and is much warmer and roomier than the Summerlite. IMO, the extra warmth and room is worth the 6 oz weight difference. But, I am 76 years old and my furnace doesn't burn as hot as it did when I was 25.

The summerlite is too slim to layer a big puffy jacket. And I'm a somewhat skinny person.

For what it's worth, I took a WM HighLite down to 19F with a MH Phantom jacket, I had to keep it 2ft unzipped cause it was too narrow. I'd rather have a Megalite or a golite z30 quilt instead.

In my opinion, the golite z30 quilt is the best buy in a sleeping system without much thought.

I have used the Summerlite down to 20f wearing merino T and leggings,WM Flash jacket and pants ,merino/possum down hat and gloves and a pair of loose socks on top of an EXPED DM7.
The last bit can make the difference…
I prefer the above to the WM Ultralite without the Flash bits because I don't need to change to get into the SB and can get up for a pee as soon as I feel like it without the usual "should I bother or not" 30 minutes wait.
I am 5'8" around 150lbs, so the 6' version is just right for me with those extra bits.
(the hat/gloves/socks do come off and then go back on at some stage…)
BTW, I am inside a ventilated shelter, if you are in a damp environment (sealed-up "4 season" non breathable tent) you could be cold
BTW, the Summerlite is noticeably warmer than the Highlite ( I had that too)

The summerlite is en rated 35F lower limit for men

Use that as a startin point …

;)

Thanks all for weighing in on this. I am looking to use this bag for 3 season, mountain conditions. I am prepared to bring insulated pats, puffy jacket etc to go to the 20's. I think this would be warm enough for me considering my experience, BUT would the Ultralight be worth the weight and size for the extra warmth? I will be carrying a MLD Burn, so I have limited space, If using the ultralight in warmer temps, is it really uncomfortable when it is in the 40's or 50's out? Thanks

I’m 6’0″, 220#. The Summerlite is a bit small for me, but I’m a side sleeper. Being a side sleeper makes a critical difference. The regular Summerlite would be too small for me if I were a back sleeper.

I’ve taken my Summerlite down to the mid 20’s F (-4C) and worn a “sweater weight” Patagonia down hoodie along with a fleece cap.

The combination of the hood on the down jacket and the hood on the Summerlite is delightfully warm. :)

Again, though, I don’t think this would work for a back sleeper.

HJ
Adventures In Stoving

Zach,

If the WM Ultralight is all zipped up, I think you will roast at 40-50 deg. If you vented it a bit, like leaving the neck area uncinched and unzipped on the side, it might be fine. But, you will be carrying 8-10 ozs of warmth that you don't really need. IMO – If u need a "one bag does it all" approach, get a Summerlite or similar 30-ish degree bag and use the puffy/fleece layers you are already carrying to augment its rating. For me, wearing warm socks, normal leggings, a puffy type jacket and a fleece beanie allows me to be comfy at about 20 deg.

For reference, I am 32yrs old, 205 lbs and healthy as a horse. AFAIK

Ryan

I started sleeping colder in my WM Ultralight. Wearing extra clothing did not work anymore. I posted here and several people reccomended getting a better sleeping pad. That took care of the problem.

Definitely use a good pad. I’m using a (first generation) NeoAir 3/4 length with my backpack under my feet. It works well.

For warmer weather (and no bugs), I sleep without a bivy sack.

For colder weather or windy weather, I find a bivy essential. The bag’s material is fairly thin, and wind will cut right through it, robbing you of your heat.

HJ
Adventures In Stoving

+1 Based on experience, as I have and have used both extensively.

"For what it's worth, I took a WM HighLite down to 19F with a MH Phantom jacket, I had to keep it 2ft unzipped cause it was too narrow. I'd rather have a Megalite or a golite z30 quilt instead."

So did I, with a slightly different clothing configuration. Wouldn't want to do it again, but I survived. Different follow on bag selection, though. I graduated to a Summerlite and have never looked back, although I did recently send it in for 2 extra oz of refill, as a concession to age. That and a WM Ultralite cover me for shoulder to shoulder season backpacking. That said, lots of good bags out there these days. I just have a preference for WM, based on personal experience.

I have taken my Summerlite down to 20f.
I usually wear a hooded fleece, hooded down sweater and merino base layer top and bottom and on warm sleeping pads.
I also sleep warm.

If the Summerlite is on the tight side for you, as it is for most, you may not benefit as much from the extra layers worn if the down is being compressed.

You do want something puffy on your head as the Summerlite hood has virtually no insulation.

Keeping you head and upper body warm makes a big difference.
And if your bag is tight, you can even fasten a down jacket over the top of the upper half of you bag.
But don't lay anything heavy on top or it will compress the down.

I always think of my Summerlite as providing only half of the insulation and always supplement with layers in colder weather.

Thanks all for weighing in on the comments. My gut feeling was with the summer light. I have used my old "30" deg bag for everything from my AT thruhike, JMT thruhike, and late summer Sierra hikes. While I have been cool at times, I have always been able to make this work. Having this as a multipurpose light weight bag fits what I need for 3 season mountainous use. The Summerlight seems like a much more puffy bag than my old one, so I know this will be warmer. I am fairly small, so the Summerlight is not at all claustrophobic, with plenty of room for warm clothes.

Just a question on having down added to an existing bag. How do you go about this? I can't seem to find WM's contact info on their site. Does anyone have this? Or did I simply miss it? Thanks again-

"Just a question on having down added to an existing bag. How do you go about this? I can't seem to find WM's contact info on their site. Does anyone have this? Or did I simply miss it? Thanks again-"

TEL 408-287-8944

Give them a call, and they'll walk you thru the procedure.

I'm glad you're going for the extra 2 oz. You won't notice the weight, and it'll give you an extra margin of comfort/safety for those unexpected mid season cold snaps.

So, how well does that work to add in an extra 2 oz? Doesn’t it compress the down? I mean it’s not like there’s a lot of extra room inside the shell, right?

And, if I may ask, what does something like that run, price-wise?

HJ
Adventures in Stoving

"So, how well does that work to add in an extra 2 oz? Doesn't it compress the down? I mean it's not like there's a lot of extra room inside the shell, right?"

Enough, apparently. WM will add up to 2 oz to a Summerlite, but no more, which would seem to indicate their thinking. Richard Nisley gave some data on the subject in a BPL thread a while ago, which indicated compression of up to 2.5 times would provide additional insulative effect. Check out the link below for his explanation.

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=26244

"And, if I may ask, what does something like that run, price-wise?"

$40, including return shipping. You pay to ship your bag to them. At least that was what I paid last winter.

I need to do this. Your bag Summerlite was noticeably loftier than mine on our last trip Tom.

Interesting. $40 bucks isn’t bad. I might have to check into “overlofting” my Summerlite. Might extend its range into the low 20’s for me. It could also extend the useful life of the bag although mine is still going strong. I freaking love that thing. Best bag I’ve ever had or used.

HJ
Adventures In Stoving

"I need to do this. Your bag Summerlite was noticeably loftier than mine on our last trip"

I think you'll find it to be $40 well spent, Craig. On my last trip, when it got down into the low 20's I needed to add my MB Extremely Lite down shirt, but then I don't have much natural insulation and I get cold now more easily in any case. I suspect it would take most folks down that far without extra clothing. Besdies, being the first kid on your block to own a Summerlite Puffay would be super cool.

BTW, just like any other gear, you only get the best performance out of a sleeping bag if used "correctly"
In this case that is having a clean sb that has had a good shake ,well before getting inside it , to get the maximum loft and is on top of a correspondingly "warm" mat.

I had WM overstuff my bag. They told me they would add about 2 oz but my bag weighed 4 oz. more after overstuffing (18.9 before, 22.9 after on a 6 ft bag). I used it down to 30 in August but had to wear my M10 to keep warm.

I seem to remember something about Summerlite not gaining much warmth by overstuffing.
The exception being times when the down has become compressed from moisture or other cause.

I suspect that a fully fluffed standard fill bag in dry weather would perform pretty close the overstuffed version.

The advantage of overstuffing could be when you in very wet conditions where the bag has absorbed moisture, with the moisture compressing the down.

Maybe an overstuffed bag wouldn't compress as much?

I have seen my Summerlite's loft shrink overnight in cool high humidity situations.

Maybe I need to look into overstuffing?