The Best Cold-Weather Sleep Sacks to Keep Baby Warm
Baby, it’s cold outside. These winter sleep sacks keep your little ones warm (and safe) when the temp dips.
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Just like Goldilocks, trying to keep your baby’s temperature just right while they sleep—not too hot and not too cold—can be a bit of a head-scratcher, especially if you live in a place where winter packs a punch. And since loose blankets in the crib are a definite no-go for safe infant sleep, what’s a parent to do?
Enter: sleep sacks designed specifically for cooler sleeping temperatures. We’re taking you through what to look for, how to dress your baby for sleep when it’s chilly outside and recommending the best sleep sacks for winter.
Kyte Baby’s 2.5 TOG Sleep Bag is our best overall pick because it hits all of the most important things on our list that we look for in a cool-weather sleep sack. It’s warm and comfortable and easy to zip. It also comes in a ton of fun colors and prints (that match Kyte’s buttery soft bamboo pajamas, too). But since climates, household insulation and personal preference vary greatly, we made sure to include a few more options to help you choose the best sleep sack for your baby.
Why Trust Babylist?
Babylist is the expert in baby; we know baby gear inside and out. We talk with parents face-to-face in our showroom and on our user panels and hear from thousands annually via our Best Baby Products online survey. We know what items millions of expecting parents are adding to their baby registries.
Firsthand professional and personal experience. As Babylist’s assistant editor and mom of two, I’ve tested my fair share of sleep sacks in a quest to find one my babies were comfortable and safe in. I also utilized insight from our senior gear editor, Jen LaBracio, also a mom of two and an editor who’s written many product guides and tested a ton of products, including sleep sacks.
Expert POV. For an expert POV, I spoke to Dr. David Berger, a pediatrician at Florida-based Wholistic Pediatrics & Family Care, and discussed all things safe sleep in relation to temperature considerations.
Sleep sack data. As Babylist’s assistant editor, I frequently dive into data on the baby products most popular with our registrants, as well as feedback from our Merchandising team—the experts curating the Babylist Shop with the best baby gear. This research guides us in selecting and testing the warmest sleep sacks to recommend to new and expecting parents.
Feedback and reviews. I reviewed sleep sack feedback from thousands of real parents through Babylist’s annual Best Baby Products survey where they talked about their favorite products, including their favorite sleep sacks for keeping baby warm enough. I also looked at reviews in the Babylist shop and spoke to parents on the Babylist team about their experiences.
How We Judged the Best Cold-Weather Sleep Sacks
The Best Winter Sleep Sack Overall
Pros
- Breathable bamboo fabric
- Smooth zipper
- Roomy in the leg area
Cons
- Hang to dry only
- Fabric pills
- Not durable
Crafted from ultra-soft bamboo rayon, this sleep bag is designed to provide the ideal warmth for rooms between 61 to 68°F—no extra blankets needed. With a 2.5 TOG rating, it’s thick enough to keep baby warm without overheating. And since it’s made from bamboo, it’s also breathable and gentle on sensitive baby skin. And when we say it’s super soft, it really is. It’s one of the most commonly mentioned things parents love about it.
The sleep sack zips up diagonally and there’s a “zipper garage” to tuck it into so it doesn’t scratch or bother their neck and chin. The bottom is roomy enough for them to stretch out and move around as they wish, and some parents mention their little ones are able to fit into them for quite a while. “It’s super long, [so] our petite 2-year-old will get to use it all the way up to when we transition her to regular blankets,” one Babylist parent said. And what about those middle-of-the-night diaper changes? There’s another zipper across the bottom for that.
While it’s machine washable, Kyte recommends you skip the dryer and hang it up instead—which also happens to be one of parents' biggest complaints. Even after following the cleaning instructions, a few parents note that the material starts pilling. This is when the fabric develops a bunch of little fluff from friction ( it’s actually somewhat common among bamboo textiles). It doesn’t affect the functionality of the sleep sack; it just means it’ll look well-loved (and worn) sooner rather than later. One Babylist parent noted, “I wash it in cold water on delicate and air dry it and it’s already [pilling].”
Most Affordable Winter Sleep Sack
Halo SleepSack Wearable Blanket (Micro-Fleece) - Penguin Pals, Small
From $29.99Pros
- Easy to put on
- Wide range of sizes
- Affordable
Cons
- Fleece isn’t the softest
- Inverted zipper can be tricky
Sleep sacks are one of those things you’ll probably buy a few of to rotate through (think one to wear, one to spare). Finding one your baby loves that’s *also* easy on the wallet is a big win. We love this Halo fleece sleep sack because it’s soft, warm and affordable. Though it’s made of micro-fleece, it’s just thick enough to provide warmth without making your baby too hot. Each brand has different criteria for TOG ratings (more on that below), and according to Halo this one is 1.0. While that’s typically not considered suitable for cold weather, the fleece material makes this one feel warmer than a 1.0 TOG sleep sack made of cotton or bamboo. (You can also pair it with fleece pajamas for added warmth.) Another thing we appreciate as busy parents is that it’s both machine washable and dryer friendly—just be sure to turn it inside out.
While many parents like the inverted zipper, some find it tricky. "You have to get the zipper ends together at the top while dealing with a squirmy baby,” one Babylist parent said. While it’s a great affordable option that washes and holds up well, we did notice it’s not as well made as the Kyte or Ergo options, but that’s to be expected since Halo has a lower price point.
Best Winter Sleep Sack for Extra-Chilly Temperatures
Pros
- Slim fit and stretchy
- Two-way zip
- Ideal for colder climates
Cons
- Pricey
This jersey sleep sack is one of our gear editor’s favorite sleep sack picks because it’s warm, and unlike the typical sleep sack fit, it mimics the same feeling as a snug swaddle. So many Babylist parents rave about noticing their babies sleeping well once they start using this. One even said, “Wish they made these in adult sizes!” It has a 2.5 TOG rating, which ergoPouch says is ideal for nurseries between 61-71 degrees, giving parents peace of mind that baby is warm and cozy enough for a good night’s sleep “[It’s] perfect for winter without doing the whole guessing game of if your baby is still cold,” one Babylist parent said. We also liked that this sleep sack's fit is slim and stretchy. It’s a nice option for transitioning straight from swaddling since it mimics that snug fit.
There aren’t many negatives to note about this sleep sack, aside from the price, which is on the higher end. A few parents found the armholes on this jersey version smaller than in the cotton option, and some noticed that they shrunk a bit after being thrown in the dryer. The brand recommends tumble drying on low and with proper care and cleaning, these sleep sacks should be able to last a while.
Best All-Season Sleep Sack
Woolino 4 Season Ultimate Baby Sleep Bag - Gray, 0-2 Years
From $109.00Pros
- Wool is naturally temperature-regulating
- Grows with baby
- Can be worn year-round
Cons
- Most expensive on the list
- Takes a while to line dry
There’s a reason people in colder climates prefer wool fabric—it’s a natural material that keeps you cool and dry when it’s warm and nice and cozy when it’s not. The same idea holds true for this all-season sleep sack. It’s made from breathable Merino wool and naturally regulates your baby’s temperature in any environment. (The outer layer is made from organic cotton so it’s not itchy.) We also love that it’s not thick or bulky and that it features shoulder snaps and a two-way side zipper for easy dressing.
Parents’ biggest gripe is the price: It’s over $100 for one sleep sack, which isn’t ideal if you want to buy a backup or two. However, you might find it’s worth the investment since it’s designed to fit from two months to two years and it can be worn year-round.
A few parents noted it has a distinctly wooly smell when wet, which is to be expected. You’ll just want to make sure you get it nice and dry after washing. Tumble dry with no heat is okay, but the brand reocmmends hang drying whenever possible (though it takes longer than most materials). But wool, by nature, is self-cleaning since it has naturally occurring antimicrobial properties (read more here if you want to dive into the specifics) so it doesn’t need to be washed as often as other fabrics.
Best Winter Sleep Sack for Swaddle Transitions
Love to Dream Transition Bag Original 2.5 TOG Transition Bag Original
From $59.95Pros
- Unzips to transition to arms out swaddling
- Warm quilt-like feel
- Two-way zipper
Cons
- Only available in two sizes
Some babies simply won't accept their arms being swaddled at their sides (mine included), which is why we love this Swaddle UP transition sleep sack. It allows baby to sleep with their arms inside the sleep sack but positioned near their head. Once they’re rolling and it’s no longer safe to restrict their arms, you can zip the handpieces off and it turns into an arms-out swaddle. This 2.5 TOG version has a quilt-like feel, keeping them cozy and comfortable in rooms between 61-68 degrees.
This sleep sack isn’t suitable for newborns since it only comes in three sizes: medium (13-19 lbs), large (19-24 lbs) and extra-large (24-32 lbs) and some colorways only come in medium or large. Though it’s on the pricier end, Love to Dream recommends washing after each use (so you might want to buy a few to rotate). Babies also love to put their swaddle-covered hands in their mouth, and a few parents note that part especially needs to be washed frequently. But the good news is, this is pretty low maintenance to wash. It’s machine-washable and dryer-friendly.
Most Comfortable Winter Sleep Sack
Pros
- Down alternative fill
- Easy diaper change access
Cons
- Fabric prone to pilling
This sleep sack literally feels like a down blanket, which is why we’ve named it the most comfortable on our list. With a TOG rating of 2.6, it’s suitable for the chilliest rooms (within the 58-70 degrees Fahrenheit range).
It's made of a bamboo rayon material similar to our Kyte pick but feels more duvet-like thanks to the “down alternative” fill that’s unique to the brand. Parents say they not only love how soft this pick is, but how convenient it is for diaper changes. The zipper runs across the entire bottom of the bag all the way up to baby’s hips, so you have plenty of space to change a diaper without removing them from the sleep sack.
What is a sleep sack?
A sleep sack is like a mini sleeping bag for your baby or toddler. Also called a wearable blanket, a sleep sack helps to keep your baby stay warm in their crib without using loose blankets. Most sleep sacks feature zippers or snaps for easy on/off and quick diaper changes. While there are a few options that do feature sleeves, the majority of sleep sacks do not have them and they’re meant to be worn over your baby’s pajamas.
Why use a sleep sack? Because your baby will likely get chilly overnight, especially if you live in a cooler climate, but putting things like blankets or quilts in the crib doesn’t align with safe sleep practices. Check the American Academy of Pediatrics (AAP) safe sleep guidelines for a full breakdown of the do’s and don’ts of safe baby sleep.
Sleep sacks are the perfect answer to keeping your baby warm and safe throughout the night.
How should a sleep sack fit?
Be sure the sleep sack you choose is sized correctly for your baby. Test out the collar and pull it up to be sure it doesn’t cover your baby’s nose or mouth while they are lying on their back. Be sure the arm and neck openings aren’t too big. Extra material below baby’s feet is fine. And lastly, Dr. Berger says baby should be able to stretch and lengthen their legs; it shouldn't be tight. There should be enough space in the hip area for them to move around freely and comfortably to ensure proper hip development.
How should I dress baby for sleep?
The key to dressing a baby for sleep is to avoid any extremes—you never want your baby to be too hot or too cold. An easy way to tell is to touch their ears or their neck. If their ears are red or hot and their neck is sweaty, your baby is likely too warm. If they’re feeling cold, it’s probably time to add a layer. Dr. Berger says if parents are comfortable, baby should be too. “As a warm-blooded mammal, we have the ability to [regulate temperature], as long as we're not exposed to the extremes.” He also stressed the importance of trusting your instincts: “Use that as your best tool.”
Since sleep sacks designed for cooler temperatures are thick and warm, so you usually only need one layer underneath, like a long-sleeve footie.
What does TOG mean?
TOG is a term you’ll see mentioned in many sleep sack descriptions, especially those designed for cooler temps. It stands for Thermal Overall Grade, which indicates how much heat the fabric retains and is graded on a scale. But since TOG isn’t regulated by any one entity, it’s important to look at your baby’s particular sleep sack brand’s chart to help you figure out which one is right for your baby’s sleeping environment.
Here are the different TOG scales for the brands on our list:
Kyte: .5 to 2.6
Halo: .5 to 3.0
ergoPouch: .2 to 3.5
Gunamuna: .5 to 2.6
Woolino: doesn’t have a TOG; their sleep sacks are suitable for rooms 63-75 degrees Fahrenheit
It’s important to note that TOG only means how warm the sleep sack is; it’s not a measure of weightiness. “I would think of it as this: if the environment is cold, you want something a little thicker [but] not necessarily heavier,” says Dr. Berger. Most experts and the AAP do not recommend things like weighted sleep sacks. “There really should not be [anything heavy] that's lying on a baby.”
Sleep sacks with a higher TOG (2.5 and up) are more insulated and meant for cooler temperatures, while lower TOG sleep sacks are lighter-weight and better suited for warmer climates. Dr. Berger gives the example of sleeping with just a top sheet in warmer weather versus something like a duvet in the chilly months.
What to look for in a sleep sack
When choosing the best winter sleep sack for your baby, keep these things in mind:
Nursery temperature. How cool does your baby’s sleeping space get overnight? (The recommended temperature is between 68 to 72 degrees Fahrenheit or 20 to 22 degrees Celsius.) The cooler your nursery, the higher the TOG sleep sack you’ll need.
Your baby’s temp. Does your baby tend to run hot or cool? Your little one’s internal heater will also affect choosing the best winter sleep sack for them.
Budget. Winter sleep sacks can get pricey. If you want to be able to use yours for as long as possible, invest in one that works from the early months through toddlerhood.
Sources
Babylist content uses high-quality subject matter experts to provide accurate and reliable information to our users. Sources for this story include:
Dr. David Berger is a board-certified pediatrician at Florida-based Wholistic Pediatrics & Family Care.
