Sleeping bag temp rating

Here is a roomy, light 25° bag:

Montbell UL SS #2

I'v seen them for in the $310 range. I have the #3 and I like it.

Temperature Rating: 25 F / -4 C
High quality 800 fill power down
15-denier Ballistic Airlight fiber nylon
POLKATEX® DWR treatment
Max User Height: 5ft. 10in.
Inside Shoulder Girth: 53.2” – 70.9” (it stretches)
Inside Knee Girth: 42.8” – 57.1”
Stuffed Size: 5.8” x 11.5”
R/ZIP/ L/ZIP
Weight: 1 lbs. 12 oz.

OR
Montbell Spiral #3

In the $220 range
Temperature Rating: 30 F / -1 C
High quality 800 fill power down
12-denier Ballistic Airlight fiber nylon
POLKATEX® DWR treatment
Max User Height : 5 ft. 10 in.
Inside Shoulder Girth : 56.7"~68"
Inside Knee Girth : 45.7"~54.9"
Stuffed Size : φ5.3" x 10"
Color: BASM(Balsam)

Weight: 1 lb. 3 oz.

If you are not going to be high in the Presidential Range, it will be warm enough with the clothes you will be carrying with you anyway.
BTW…welcome back, sounds a lot like me (mid 50s now)

Dwight:

3-season covers a wide temp range, esp. when applied to all elevations of an entire continent. So stating the obvious, much depends on where you hike. If you frequent the more northerly latitudes and higher elevations, 30F may be insufficient. Down here in the Sierras of southern Cal — 30F in summer is usually OK. In the lowlands of the south and southeast, 30F may be an overkill.

If 30F suits your range, then I second MontBell up above. The rating is spot on for the average sleeper. And if you don't mind a fiery red color, the Western Mountaineering Summerlite rated 30F is also a champ. WM temp ratings tend to be conservative — meaning an average sleeper should still feel comfy down to 25F.

Do note that most "name brand" bags tend to exaggerate their temp ratings — and then they also under-report on the weight of their bags! For TNF, Marmot, Sierra Designs, etc. — expect a 5F or so of "warmth optimism". For cheaper brands like Slumberjack — expect at least 10F exaggeration.

Dwight, I think your thoughts are right on the money. If your 3 season lower temp is 30 degrees expected with lows in the 20's or even upper teens then I would buy a 30 degree bag and use clothing to extend the rating on the rare occasion it gets that cold. All this assumes your comfort level matches the bag you are buying (i.e. cold sleeper vs hot sleeper). I purchased a Marmot Hydrogen just for this purpose. It is rated to 30 degrees, I’ve used it down to 20 degrees under a tarp and in a bivy and was fine with extra clothes. In a pinch this bag could have gone 10-15 degrees easily. I see no reason to carry all the extra weight all the time when you only occasionally need it, especially considering your sleeping bag is typically the heaviest thing you will carry.

Jamie

Every reply contains excellent advice. Thanks all. It's good to hear what I was thinking, that the need for a 20-degree bag, is mostly driven by the large number of people on this site that hike in the mountains out west. I'll be hiking mostly in Michigan, and when and if I make it out west I'll buy a colder bag.

I am looking at the Hydrogen and the Megalite, both 30-degree bags. My shoulders are 60-inches around and I've always had trouble fitting my shoulders in normal sleeping bags. This is the first I've considerd the Montbells, I'll be taking a closer look at them now.

I won't buy a North Face. I did most of my hiking in the seventies when The North Face was the absolute Top Of Line, premier backpacking equipment. But like all things, they've changed and now seem a little more focused on making street gear.

Again thanks for all the help. It makes it a little less nerve racking to spend $300-plus on bag.

dwight, i noticed you said you were looking for a roomy bag. this gave me an inkling that you may be tall. the montbel bags are cut very short length-wise. so please pay close attention to length before ordering. i'm pretty sure their regular only goes to 5'10", whereas most regular bags go to 6". just wanted to give you a heads up…

It all depends on where you are doing your backpacking and what *you* consider to be 3 seasons, whether your backpacking season starts on the first day of Spring and ends on the last day of Fall, or whether your backpacking season starts as soon as the trees start budding and ends when the last of the trees lose their leaves for the season.

Additionally, it should be understood that while many people do own just one nice sleeping bag for "3 season" use, many posters on BPL own (and productively use) a sleeping bag for every micro-climate to be found within the lower 48 in any of the 12 months of the year.

For the regular type of backpacker, what it boils down to is, do you want to be (would you plausibly find yourself) in a situation in which you only have a 30 degree bag (assuming it's accurately rated, which most bags aren't), only to have the actual low for your trip get down to 25 degrees even though it was forecasted for (and you'd prepared for) a 35 degree low at coldest? This could lead to loss of sleep and some discomfort when a few more ounces of down would have allowed you to sleep through the night. Even worse, though, is maybe you can live with a minor discomfort like that, but what happens when you find yourself on a backpacking trip in mid-November (still Fall, still "3-season"), but a front blows in, the overnight temps drop down to 10 degrees and it starts snowing? Will you be more comfortable in your 30 degree bag than you would if you'd brought a 20 degree bag?

Another thing I've found is that 30 degree down bags just kind of suck in general due to their skimpy loft–and I say that as a proud Summerlite owner, but in Spring and Fall I really do appreciate the extra half inch of loft and the draft collar that a 20 degree bag provides. (Hence, you might point out, the humble name of that bag: "Summerlite.") Then again, I only have this kind of opinion of 30 degree bags because I thought I'd be able to comfortably use mine for 3-season backpacking…