Hello Winter, Goodbye Coats!

Puffy winter coats and car seats don't mix

Puffy winter coats and car seats don’t mix

With the winter days headed our way, we’d like to talk about staying warm and safe in the vehicle at the same time. Wrapping your kiddo in the warmest jacket possible seems the obvious way to stay warm but puffy coats are not the safest option when it comes to car seats and booster seats.

Why is it Unsafe to Wear Some Coats in the Vehicle?

For your child’s car seat to offer the maximum protection in a crash, the harness or seat belt needs to be as close to the child as possible. The more layers of padding or clothing between a child and the harness, the harder it is to properly fit the restraint to the child. The harness can end up fitting to the thick coat, and in the event of a crash, all that extra air is forced out between the layers, leaving the harness too loose to protect a child. A loose harness, at best, means extra crash time on the child, and at worst, could mean ejection from the seat. This principle also applies to children riding in boosters and adults in seat belts.

How to Check

pinch test, winter coat, coats in car seats

Slack left in the harness when winter coat is removed

Here’s a great visual of how loose the car seat’s harness could be in a crash with this coat on the child. We also see the way to wear that coat safely in the vehicle.

A simple test can help decide if this coat is too bulky to go under the harness.

  1. Put the coat in question on your child. Head out to the car.
  2. Buckle the child into the car seat.
  3. Tighten the harness enough to remove all slack at the child’s collarbone.
  4. Unbuckle the child from the car seat without adjusting the harness.
  5. Take off your child’s coat, then buckle the child back into the car seat.

In this case, we see that her cute and puffy coat created quite a lot of potentially harmful slack in the harness!

Try it in Reverse

Here’s another way to look at that test.

  1. Without a coat on, secure your child in their car seat. Tighten the harness as usual so no webbing can be pinched at the collarbone.
  2. Remove the child from the car seat without adjusting the harness.
  3. Put the child’s coat on, then try to buckle them back into the car seat.

Note: properly fitting fleece jackets or sweatshirts do add a bit of bulk to the child’s body and will often require a little harness adjustment.  The key here is harness length that remains appropriate to the child’s compressed clothing, compared to ‘dangerous amount of extra slack intro the harness via an uncompressed puffy jacket.’

In many cases, you’ll see that coats introduce a potentially dangerous amount of slack to the harness. The pinch test can determine how much slack is acceptable.

Aftermarket Products

Bundle Mes and car seats don't mix

Slack left in harness when Bundle Me is removed

For the most part, we’re not fans of aftermarket products. FMVSS213, the federal standard for car seat safety testing, doesn’t apply to these products so there’s no consistent way to determine whether or not any particular product is safe. While these products are marketed as “crash tested”, there is no way to crash test them since there are no federal standards for them to be tested against. They not only add bulk, but often interfere with correct harness routing. That’s why we advocate for using only the equipment that’s shipped with your particular car seat and not adding anything to the seat.

Here’s an example of a popular product and a look at why it’s potentially an unsafe option — the JJ Cole Bundle Me. We added the Bundle Me to this little cutie’s car seat, adjusted the harness, then removed the Bundle Me. Look at how much slack there is in the harness now!

What it Really Takes to Stay Warm

Another important consideration is that children do not need to wear all those layers while in the vehicle. Even if it takes a while for the vehicle to warm up, when it does, the child can become hot, sweaty, and generally cranky if they are dressed in too many layers. Usually, even the tiniest of babies need at most one more layer of clothing than their parents are wearing to be comfortable.

So often we see caregivers envelop their babies in a onesie, socks, fleece pajamas, a hat, a blanket, and then inside a Bundle Me in a warm car while the caregivers are wearing sweatshirts.


If bundling your child into a great swath of puffy jackets isn’t the safest option, what can you do? Here are some popular options that don’t interfere with the car seat’s harness.

Shower Cap Style Cover

winter coats, pinch test, harnessed seat, shower cap cover

Safe shower cap cover for rear facing only car seat

The shower cap style cover goes over the top of a rear facing only car seat. This type of cover doesn’t interfere with the harness at all and is easily removed if the child starts to get too warm. Some styles include a zipper to help adjust the temperature as well. Some manufacturers advise removing this style of cover when in the vehicle to ensure the child does not overheat and the seat clicks into the base properly.


Thin fleece jackets are a great way to stay warm and safe

Well-fitting fleece is our go-to option because it’s thin enough to work well car seat harnesses yet warm enough to keep the child comfortable.

Fleece one piece suits may be a good option – be sure to check the fit

Some manufacturers make relatively inexpensive one piece fleece outfits. They come in thinner and thicker varieties. These can be a great option, especially for the tiniest of passengers. This type of garment isn’t a snow suit by any means — we wouldn’t suggest using it for a day on the slopes, but in the car, it’s a great option on those windy days when blankets are a bit awkward or when you’ll be getting in and out of the vehicle throughout the day.

Other Options

Putting a jacket on backwards over the harness is an easy way to stay warm

Backwards Coat

This backwards coat trick works well for older kids (and adults too!). Here’s how it works:

  1. Secure the child in the car seat without their coat on.
  2. Once the child is strapped into the car seat, put their coat on them backwards

This method keeps the harness snug to the child and allows the child the freedom to remove their own coat if they become too warm.

coat winter

Safe winter coat use in a booster seat

Open Coat

Some coats and most fleece jackets are thin enough to wear safely in the car. To keep a safe distance between the harness or vehicle seat belt (for booster riders), unzip the coat.

  1. Have the child put on their coat, but don’t zip it up.
  2. Load the child into their harnessed car seat.
  3. Once the harness is secure, zip the coat up over the harness.

For booster riders, this method also works.

  1. Have the child put on their coat, but don’t zip it up.
  2. Have the child climb into their booster seat and secure the seat belt.
  3. Once the child has buckled themselves in, zip the coat up over the harness.

This method keeps the child warm and allows the seat belt to lie flat on the child’s chest. The seat belt remains in contact with the child’s shoulder, at the appropriate place over the hips, and correctly positioned in the lap area.


Ponchos are comfy, safe, and warm!

Ponchos are comfy, safe, and warm!

There are a number of poncho options that work well with car seats.  The key feature is that the poncho doesn’t interfere with the harness — the poncho covers the front of the child while adding no extra bulk between the child and the harness.

Blanket and Hat

Stay warm with a blanket OVER the harness

Stay warm with a blanket OVER the harness

You can’t go wrong with blankets, a hat, gloves, and warming up the car ahead of time if possible. These are easy to do: after properly tightening a child’s harness or buckling into a booster just tuck a blanket around him or, if she’s perfectly capable of doing that herself, thank you, hand her her own blanket.


Car Seat Poncho


Car Seat Poncho for 7 year old and 1 year old

The Car Seat Poncho is made from fleece and doesn’t interfere with the harness. The zipper can unzip from the top or bottom, making it easy to buckle the child in.


Want something that does double duty and keeps kids warm in the winter and cool in the summer? The Noggle connects to the vehicle’s air vents and helps keep even the smallest occupants comfortable.

In Summary

There are many ways to safely and warmly transport children in car seats during the winter. Like so many parts of parenting, there is no one best option for all families. As long as you don’t introduce extra slack under the harness or seat belt, kids will be safe and warm all winter long.

Originally written by Jennifer Penick. Edits lovingly maintained in her memory by CSFTL.