No one likes getting into a freezing cold car in the winter. Of course we need ways to keep children warm in the car, especially for those first five or ten minutes of the car ride before the car heats up. But snowsuits and coats can be unsafe in the car, largely due to their bulk and and the amount of air they retain (their “puff.”) These features are why the coat keeps your body warm, but they can create too much slack in the car seat straps, which can lead to injury in a crash. Here’s a discussion of why these clothes can be problematic, how to tell if your particular outerwear is safe, a list of products The Car Seat Lady recommends for the car, and other techniques and tricks for keeping children warm in the car

Coats can cause unsafe amounts of slack in the harness straps

Most winter coats and snowsuits are like air-filled suits where no matter how tight you make the car seat straps, you can’t get most of the air out. You’ve probably tried buckling your child into the car seat in their coat and noted how it feels hard to pull the straps snug with the coat, or maybe you couldn’t even fit your child in the car seat with their snowsuit or puffy coat on.

But crash forces are extreme! They crumple the steel of the car and thus can easily push the air out of the clothes. When your child wears these items, it may seem like the car seat harness straps are straps are snug over their body, but in reality the “puff” leaves 2 to 4 inches of slack in the straps, slack that is hidden because the “puff” is not yet compressed. Two to four inches is enough for a child to slide out of the car seat in a crash! 

Not convinced that your child’s coat is a problem? Do the chalk test as shown below in this video. Not convinced that four inches is a lot of slack? Imagine wearing pants that are 4 inches too wide in the waist to a job interview, or walking a puppy with a collar that’s four inches too wide at the neck, or putting your newborn in diapers that are 4 inches too wide at the leg holes… you’re gonna care about those four inches.

What’s 4 inches to your child in a crash? A whole lot, says Miriam Manary of the University of Michigan Transportation Research Institute (UMTRI). Four inches significantly increases the risk of injury, and particularly head injury. Here’s how she studied this (the video below uses her crash test footage):

In her crash test lab she properly installed two identical car seats side by side on the crash test sled bench. The only thing she varied was the snugness of the harness straps. She buckled one dummy in properly, but left the other dummy’s straps with four inches of extra slack. 

The loose dummy’s head moved 4.25 inches farther forward than the properly buckled dummy. 4.25 inches is easily the difference between your child’s head hitting the back of the seat in front of them, or not. This is a known cause of serious head injuries to real kids in real crashes. 

The head and chest injury scores, which indicate how likely a real child would be to suffer a head or chest injury, were also significantly higher for the looser dummy because when the child is loose they can’t take as much advantage of the injury reducing safety features that the car offers, like crumpling to absorb some of the force of the crash.

Here’s an even more detailed discussion of how and why fluffy snowsuits, inserts, sleeping bags, etc, affect the car seat’s performance. We go over why these items can be dangerous for the car seat. 

Is Your Child's Coat or Snowsuit Safe for the Car Seat?

We include a list of car seat safe products below, but we can’t possibly list every jacket and snowsuit that are safe for the car seat. You can quickly assess if yours is or isn’t safe by doing our very simple Chalk Test. All you need is your car seat, your child, the snowsuit or jacket you’re concerned about, and a piece of sidewalk chalk. Here’s how to do it:

For a little more detail on how we tighten the harness straps, take an extra minute and watch this video.

The Car Seat Lady's Recommendations for Keeping Kids Warm AND Safe

The Art of Layering

No one is suggesting that your child ride in a t-shirt and shorts in winter! Dress your child in two to four thin, tight layers in winter. How many layers to use depends on the outside temperature, if you can warm your car up ahead of time, how cold/warm your child tends to be on average, and what other products you may be using to keep the child warm in the car. The goal: a comfortable child in the car – not too cold and not roasting like a turkey on Thanksgiving! 

We’ve used OldNavy toddler fleece leggings for our kids for several winters now. Usually under $6, they’re great for layering under jeans and other not-so-warm pants and are much cheaper than buying fleece lined pants. The leggings are only available in the toddler girls section but they fit toddler boys great too. 

As you can see, we recommend using a combination of onesies, zip up sweatshirts, leggings, pants, and a jacket (one safe for the car seat of course) to keep kids warm. Don’t forget the hat and socks!

The Car Seat Lady's Favorite Outerwear (in no particular order)

You can find a detailed discussion of different techniques and types of outerwear and warming wear below, in case you’re not sure what the best type is for your travel needs. You’ll definitely want to read it if you’re not sure what’s the difference between a shower-cap style car seat cover vs a snowsuit vs a sleeping bag style item. 

Note that for many coats and snowsuits you must buy your child’s correct size. Larger sizes will be too bulky or too long to be safe in the car seat.

The Nido is a hooded, footed, swaddly snowsuit that’s 100% car seat safe. The hole in the back allows it to be put on after baby is buckled snug! Works with infant and convertible seats and also for babywearing (facing out.) 

We used the Nido with one of our own and loved how easy it was to take baby out in the cold. Simply dress baby in 2-3 thin layers and put the Nido on after baby is buckled and you’ll have a happy, toasty baby. The Nido is so warm that we recommend opening it up in the car so that baby doesn’t get too toasty. 

Get the quilted (warmer) version in large, so that it will last through two winters (this is one product where size does not affect safety in the car seat.) 

The 7AM Enfant Cocoon is a “shower cap” style cover that fits over the infant car seat and is 100% car seat safe as it does not go under the baby or under the straps. The Cocoon is helpful for keeping wind and snow off baby as you’re walking outside and for keeping strangers’ hands away too! If you’re looking for the warmest option, choose the Nido instead. For city parents taking taxis/Ubers, note that Cocoon blocks the seat belt path – so choose Nido instead.

The Patagonia Hi-Loft Down Hoody is very puffy, but when sized appropriately you can compress all the puff when tightening the child’s harness straps, making it safe for the car seat. Insulated with super warm 600-fill-power 100% Recycled Down (duck and goose down reclaimed from down products). Available in toddler & big kid sizes. The thinner Patagonia Down Sweater jacket is also car seat safe and layers nicely. Note: you’ll need to pull the straps snug an extra time or two more than usual to make sure you’ve pushed out all the air in the Down Hoody. 

These Columbia fleeces are workhorses in our family and we LOVE that they’re under $25 and wear well. They’re thick fleece but fitted snug to the body, which avoids unsafe bunching of fabric under the car seat chest straps. Available in sizes 3 mo to adult in boys & girls. Boys: Steen Mt II Girls: Benton Springs

We’ve used Road Coats for our kids for several winters and think they’re awesome. These well-made, durable down coats are 100% car seat safe when sized appropriately. Road Coats keep kids warm on the playground in 30 degree weather and are a fabulous option for parents who don’t want to deal with taking coats on and off when going in and out of the car. Totally worth the price! Available in sizes 12 mo and up

The Road Coat works using an innovative double zipper system and split collar which allow the car seat straps to fit snug to the child’s body without adding any extra slack to the harness. Heavy duty chunky zippers mean even a 3 year old can zip it on their own. For fashion-focused folks, know that it looks like a regular coat, not like something designed for the car seat.

For down snowsuit fans, the OneKid Road Coat Snowsuit is perfect! It’s 100% car seat safe when sized appropriately. A thin inner and puffy outer front layer closure provides easy access to the car seat harness while eliminating puffy layers between the seat and baby’s body, and a split collar construction with soft hook and loop closure allows harness straps to pass to front and to lay flat on shoulders. This snowsuit is especially helpful for those who babywear while walking/at the playground in winter and then need to transfer the baby to the car seat for the drive home, because it avoids needing to take jackets/snowsuits off a (potentially) sleeping baby. 

Safe for the car seat when sized appropriately, the North Face OSO Infant one-piece will keep your baby looking cute and feeling toasty.

The Snowtop II Bunting is the perfect warmth so baby doesn’t overheat too quickly in the car. It’s safe for the car seat when sized appropriately and at under $30 and available in size 0/3 months and up, it’s the perfect layer for chilly days.  

When sized appropriately, this one-piece is safe for the car seat. It’s made of lightweight 100% recycled microdenier polyester fleece. 100& Fair Trade Certified™ sewn.

Designed for babywearing, the 7AM Enfant K-Poncho is a fitted blanket that can also cover baby in a car seat as well. The K-Poncho features a hood that is reversible and removable. The plush lining of the K-Poncho will keep baby toasty. The K-Poncho works great on carriers like Ergo, Tula, BabyBjorn – and is extra wide in the legs to keep toddlers’ legs covered and warm.

The Zutano Elf Fleece Romper is a great thin top layer for babies in infant seats who will be covered with a blanket after getting buckled snug.

Ways to Keep Kids Warm in the Car

Some parents prefer snowsuits, others like fleece suits, and others like blankets and ponchos. Here are a bunch of different ways to keep your kids comfy and safe during winter car rides. Not all require car seat specific products, and many techniques are applicable to newborns up to school-aged kids. 

Double Swaddle

It’s safe to swaddle babies OVER the straps (never swaddle under the car seat straps). Use a thin receiving blanket first – this will give you a nice tight tuck that will be a good air barrier – and then add a heavier blanket and if it is cold, tuck that nice and tight around the baby and under their feet. Swaddling both warms and soothes babies. See this video for a how-to on car seat-safe swaddling.

Note: as the car warms up, you will want to remove the heavier blanket so your child does not overheat.

Backwards Coat Trick

Make sure the child is wearing a few thin, tight layers and have them go to the car either carrying the coat, or wearing it unzipped. Then buckle them and get the straps snug with the coat off. After the straps are snug, have the child stick out their arms and put the coat on over top of the straps. You can tuck the coat along the child’s chest to keep them extra warm. When the car warms up, the child can easily pull the coat off so they don’t overheat.

Unzipped Coat Trick

This is perfect for thin coats, because it gets rid of half of the fluff AND if the child gets warm during the car ride, they can unzip the coat to cool off a little.

With bulky or puffy coats it’s still best to remove the coat completely – but, if you can’t or won’t remove the coat completely, this is a way to at least eliminate half of the fluff of the coat… which makes even the bulkiest of coats safer for the car seat as the straps are snugger to the child’s body with only half of the coat under the straps.

Shower Cap Style Infant Car Seat Covers

These “shower cap” style covers fit over the infant car seat (they do not go under the baby or under the straps in any way) and use an elastic rim to stay in place. Some parents really like these. We aren’t huge fans since they don’t keep the baby that warm due to the large gap between baby and the cover, which means you still need to dress baby warmly and have a blanket or two over baby in addition – and then the baby can get too hot in all of this when the car finally warms up. They are helpful for keeping wind and snow off baby while walking outside and for keeping strangers’ hands away from baby.

If the car will be warm for most of the ride, be sure to open these up or remove them so the baby won’t overheat in the car.

For frequent taxi/uber users: If you’re going in and out of taxis, Ubers, etc you will NOT want to use a cover like this because it covers the car seat’s seat belt guides. That means you’ll have to take the cover off in order to install the car seat without the base. The 7AM Enfant Nido or a safe-for-the-car-seat snowsuit like the Road Coat snowsuit are ideal for parents who will be installing the carrier without the base. 

Here are a few “shower cap” style infant car seat covers currently on the market:

7 A.M. Enfant Car Seat Cocoon 


Jolly Jumper Arctic Sneak-a-Peek 

Skip Hop Stroll & Go Car Seat Cover 

Multi-Use Covers (for the car seat, babywearing, strollers

The Car Seat Lady loves babywearing (just not in cars, of course!) and we know that an essential piece of gear for winter babywearing is a warm carrier cover to keep baby’s legs and feet warm.

We’ve used the 7AM Enfant Pookie Poncho and the CatBirdBaby Winter Baby Carrier Cover and loved them both. We’re excited about 7AM Enfant’s new K-Poncho which is wider at the hips and leg area like the CatBirdBaby one – which means it will fit big kids in ergonomic carriers for longer. These can be used as blankets on top of a child in a car seat or on strollers as well.

Sleeping Bags for Car Seats and Strollers

Most sleeping bags, like the Bundle Me, are NOT safe to use in the car seat.

Why are they unsafe in the car seat? They have a layer of fluff that goes UNDER the baby’s body… which is exactly where you do NOT want to add fluff. Because these sleeping bags are sold separately from the car seat, they are not required to meet any safety standards, are not required to undergo any crash testing on your child’s particular car seat, and most importantly their use is strictly prohibited by most car seat manufacturers.

The bottom part, while not safe for the car seat, is absolutely safe to use in the stroller as strollers don’t get into crashes.

In the picture above, the fist worth of room that you find with the sleeping bag removed is exactly what the straps would feel like in the instant of a crash when the sleeping bag is in use. The crash forces will compress all the fluff in the sleeping bag, making it as if the sleeping bag didn’t even exist, and the straps therefore way too loose for the baby’s body.

If you have a sleeping bag and would like to use it in the car seat, you can cut it to remove the fabric behind the child’s back and under the bottom, leaving behind a safe product as shown in this video. Please note that if you cut the product, you’ll need to sew the cut edges. Otherwise there will be filler material coming out, and that’s a choking hazard for the child.

There are some sleeping bags made by 7AM Enfant – the 212 blanket (which between us is the best stroller blanket on the market), LambPod, BeePod, PlushPod, GlacierPod – that have removable back panels to try and eliminate adding slack under the harness. You will need to try before you buy to see if these will fit your child’s car seat properly. The hole needs to be big enough to fit from the crotch buckle all the way up to the highest shoulder strap slot your child will be using. If the hole is smaller than this, then the product will introduce slack in your child’s harness straps. You will also need to be careful if using with a baby who can not sit upright unsupported that there isn’t too much puff behind the head area with the back panel removed in the car seat as you don’t want to do anything that could push the baby’s chin to its chest as babies can’t breathe well like this.

There are other 7AM Enfant products – the Polar Igloo and Le Sac Igloo – that are designed to allow you to use a part of them safely in the car seat. With these, you leave the bottom part of the sleeping bag in the stroller, and you zip the top part off to use on the car seat. The top part is specially designed with a fleece sleeve at the bottom that fits over the foot area of the car seat. Another way you can use the top part is to tuck the baby’s feet into the fleece sleeve and use the top part more as a bunting for the child (again, all the fluff is over the straps in this scenario – making it safe for the car).

Note: Just the top part of the Igloos are safe to use in the car seat (despite what some of the marketing images on the company website may show). The bottom part, while not safe for the car seat, is absolutely safe to use in the stroller as strollers don’t get into crashes.

Fleece Suits and Rompers

Many parents enjoy using fleece one piece suits for babies & young toddlers and we’ve found a few that are safe for the car seat when properly fitted to the child. If you order the next size up it will not be safe as you’ll have extra fleece bunched up under the chest straps. These have turn over cuffs at the feet and hands and are available in sizes from 0-24 months.

Here are a few car seat safe fleece suits currently on the market:

Super thin packable down jackets

Some of the REALLY thin down jackets will also work so long as they are thin AND properly sized for your child. Make sure they stop at the child’s waist – as longer coats will not be safe as there is too much that bunches up under the hip straps and between the crotch buckle.

3 in 1 jackets

Those featuring a removable fleece insert are great for the car since you can unzip the outer layer, remove it, and leave the fleece on under the straps. The outer jacket can be used over top of the straps (the child can use it as a blanket, or put their arms in the sleeves so it is worn backwards).

Please note that jacket also needs to be short. If it goes below the hips it will definitely be too bulky for the car seat.


Ponchos are a safe way of keeping kids warm in a car seat when you flip the back over the top of the car seat and keep the front over top of the child’s straps (therefore there is NO part of the poncho that is under the child’s harness straps.

We know many people use car seat ponchos and like them a lot. In our experience with our own kids we didn’t end up using ponchos as 1. our kids didn’t like the hood on during the whole car ride and 2. it was hard to buckle the child as the poncho was either flopping over the straps and hiding them (when unzipped from the bottom), or it was flopped over the baby’s face during buckling (so that you could see what you were doing to buckle the straps) and the kids hated it over their faces. 

The KidCozy II works on car seats, strollers, and while babywearing (both facing in and facing out thanks to its reversible hood design) and fit infants through 4 year olds. These can be worn with the hood off if the child desires.

Wearable Blankets

The Bonchos is a wearable blanket with a comfortable neck hole AND holes for the hands… allowing your child to stay covered but have their hands free for playing. Also works in strollers and on baby carriers (facing out). They have ones that are single layers, and ones where there are 2 layers of fabric (and will do custom orders). Works for babies and big kids up to about age 3.


Statements from the car seat manufacturers regarding winter clothes and accessories bought separately from the car seat. Excerpted from the car seat instruction manuals. Please always check your car seat’s manual for specific guidance in this area. 

Baby Trend

Do Not dress your child in bulky clothing or other garments that will hinder the harness from being snug around your baby and properly latched between your child’s legs.

Accessory products for use with the Safety Seat are acceptable for use provided that they do not interfere with the harness assembly, or the proper adjustment of the harness such that it remains tight on the child’s shoulders at all times. Thick, soft, or other compressible material in excess of 1/4 inch thick should not be placed behind or under the child or between the child and harness straps. Examples of accessory products are head support pillows or rolled blankets to add additional head support.


The use of non-Britax Child Safety, Inc. covers, inserts, toys, accessories, or tightening devices is not approved by Britax. Their use could cause this restraint to fail Federal Safety Standards or perform worse in a crash. Their use automatically voids the Britax warranty.


NEVER use clothing or blankets that interfere with fastening or tightening the harness. An unsecured child could be ejected in a sudden stop or crash! To keep child warm, place a blanket over child and restraint AFTER you have properly secured child in harness.

DO NOT use any accessories, pads or products supplied by other manufacturers with this Child Restraint. Items not tested with this restraint could injure your child.


Child must be dressed in clothing with arms and legs that will not interfere with buckling and snugly adjusting harness. Never place blankets between harness and child.


Child must be dressed in clothing with arms and legs that will not interfere with buckling and snugly adjusting harness.

Do not use accessories or parts other than those provided by Combi USA. Use of accessories or parts from other manufacturers could alter the performance of the car seat.


Never secure child in infant carrier dressed in a bulky garment or heavy clothing.


Using any non-Diono/Sunshine Kids product with this restraint; or any product not specifically approved by Diono/Sunshine Kids for use with this restraint is not allowed. Use of such products voids manufacturer’s warranty and may seriously impact the products ability to perform properly in an accident.

Dorel (Cosco, Eddie Bauer, Maxi Cosi, Safety 1st)

Dorel Juvenile Group does not recommend the use of any child restraint accessories except those recommended by DJG.


In cold weather, DO NOT dress the child in bulky clothing like snowsuits if the child is riding in a child restraint. Bulky coats/ snowsuits make it difficult to properly tighten the harness to the child, which may allow the child to be ejected from the restraint during a crash.


DO NOT use accessories or parts other than those provided by Graco. Their use could alter the performance of the car seat.


Never use clothing or blankets that interfere with providing a properly tightened harness. An unsecured child can come out of the restraint during a crash. Place blankets over child AFTER harness has been properly tightened.

Peg Perego

Use only approved parts. Use of unapproved parts can affect the safety of the car seat and cause serious injuries in an accident.


DO NOT secure an infant in the carrier with extra material, bulky clothing, or extra padding. Instead, place a blanket over the harness after properly securing the child.

Check out our Amazon list of winter gear for babies and winter gear for toddlers & up for more ideas.

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FTC Disclosure: Affiliate links are included in this page. No monetary compensation was provided, however, some of the reviewed products were supplied by the manufacturer or distributor to help facilitate the review. All opinions are those of The Car Seat Lady LLC.