If you’re not sitting down, please do; I’m about to shock you. Ready? Good.  Here’s the deal…weather forecasters are NOT right 100% of the time.

It happens, particularly in the “shoulder seasons” (early spring, late fall). You’re on day 3 of a trip, and suddenly the weather changes. The forecast had been for the 20s at night, and it plunges to 5…and you’ve got a 20 degree bag. Sure, you can survive it…but can you enjoy it?

Actually, based on our experience, you can, and with only minimal planning and gear changes. The first thing is to have a sleeping bag that adapts well to the changes, and in our opinion, that means a bag with a good draft collar; there’s probably no other single factor as important to maximizing efficiency of a sleeping bag. There’s no point in making changes to your clothing and creating extra warmth in the bag, and then having it all pumped out of the bag every time you move. The EN13537 article discusses our findings, and also how to pick a bag that’s appropriate for you. Once you have the right bag, here’s what we’ve found works to keep you warm when it’s suddenly “too cold” for your sleeping bag.

How to Sleep Warm In Unexpected Cold

1.  Carry a lightweight liner/overbag. Coccoon makes a variety of these; without question, the best warmth/weight/feel combination for backpackers is their silk liner. That one, and other liners, are available at Campmor, as well as other retailers. They pack small and light, and can dramatically improve your bag’s rating. As a bonus, you can use them in summer camping on top of your sleeping bag for really hot nights.

2.  Wash. Not your sleeping bag, yourself. After a day of hiking or snowshoeing, your body is covered with salt from your sweat. Even if you dry off, it’s still there. Salt is hydrophilic; it attracts moisture. As your skin breathes at night, it holds the moisture rather than letting it wick away from you. Moisture, in turn, wicks heat away from your body. A quick rinse off with a wet pack towel in some warm water is all that’s needed; no soap required. Or, if you carry baby wipes for personal hygiene, you can use those. We’re talking a HUGE difference in warmth, as well as getting rid of that clammy icky feeling.

3.  Carry ultralight “sleeping jammies.” We’re talking silks, or imitation silks. A set weighs a few ounces, and gives you something clean to slide into. NO salt inside them from the day (see #2). If you layer other clothing on top of them, you’ll always have moisture wicking from your body into your outer insulation layers.

4. Disposable handwarmers. When the temperature outside is low, you’re “exothermic”; meaning, your body is releasing heat to the outside. Not exactly what you want! So, put something into your bag that allows you to be endothermic, absorbing heat. Handwarmers are cheap, light, and have minimal environmental impact. If you’re sort of cold, one by your feet might be enough. If you’re sleeping in a valley and the temperature’s 30 degrees below your bag’s rating, you might have a couple down there and a couple in your core body area. If you don’t have handwarmers, you can warm up a water bottle and stick it down by your feet, but it’s tough to get the heat where you want it with a bottle, as it’s hard and gets in the way.

5.  Fleece neck gaiter. A lot of our thermoregulation comes from the back of our necks. A slight draft there can impact your comfort level, making you feel colder than you actually are. Most of us automatically assume we’ll wear a hat on a cold night; but, with a good hood on your sleeping bag, the hat may not be all that necessary. Even with a good hood, though, there’s likely to be a little cold air leaking in around your neck…cover up! Another all-in-one solution is a balaclava. Ultralight versions are readily available and well worth having.

6. Your “puffy”. When we’re in cold season, the puffy is automatically part of our gear, and it’s a great choice to wear inside your bag. Unlike a lot of insulation layers, the puffy contracts and expands to fill space, making your sleeping bag cozier, more comfortable AND more thermally efficient.

7. Eat and drink. One of the biggest mistakes people make is to not drink enough. It’s perfectly understandable. Who wants to get up in the middle of the night to pee? But, your body’s thermal processes work best when you’re fully hydrated. So, better to have to get up and shiver for a few minutes than to shiver all night long (Bonus: unexpected cold usually comes from “radiational cooling”; in other words, clear nights with no wind where all the heat heads to the stars. The view of the heavens during that midnight rest stop can be priceless!) Before you go to bed, and when you get up in the night, drink a little more and eat something…a handful of gorp, or peanut M&Ms, fuels your furnace and tells your body to go ahead and let your metabolism have a party.

8. Breathe OUTSIDE your bag. No matter how tempting it is, particularly when you first get into a chilly bag, DON’T tuck your head inside and try to recycle your warm breath. There’s a ton of moisture in your breath (that’s what you see when it’s cold), and as the night goes on, you’ll pay for a few minutes of early warmth. If you’re so cold that your face is freezing, try tucking a bandana into the remaining opening and breathing through that. It’ll hold some warmth, but let a lot of the moisture out.

If you take everything recommended here, you MIGHT raise your pack weight by a whole pound, and a good night’s sleep is worth a whole lot more than that. Half of the battle is being prepared. The other half is to admit that you’re getting cold and do something about it. I woke up cold around midnight the other night, as I hadn’t washed up and was feeling clammy. I wanted to stay in bed, but I knew that if I did, I’d be miserable all night. Instead, I toughed it out for  5 minutes of chill as I washed up. Then, I dropped off to sleep again quickly and spent the night warm, comfortable and happy. Take pride in enjoying your trip, not in suffering, and you’ll find you’re happy to spend a lot more time in the woods!