When winter hits, keeping little ones warm in the car becomes a priority. But so does keeping them safe on the road! Today, I’m diving into how to follow the best car seat guidelines, meet car seat requirements, and use the car seat the way it was crash-tested. We want to make sure your child is not only warm, but truly safe in the seat.

Why This Matters

One of the fundamentals of child passenger safety is that the seat should fit the child’s age/weight/height, fit the vehicle, and be used correctly every ride (both correct installation and correct use). When a child is snug in a car seat, the harness is in direct contact with their body, which is exactly how the seat was designed and crash-tested to protect them.

But what happens when you layer up with a bulky winter coat and try to buckle that harness? The extra bulk can compromise fit and performance, and thick coats under harness straps are problematic.

What the Research and Guidelines Say

• The National Highway Traffic Safety Administration (NHTSA) tells us to select a seat based on your child’s age/size, install it properly, and use it every time. Using the seat exactly according to the manufacturer’s instructions (installation + harnessing) is essential.

• Bulky coats under the harness can introduce slack in the harness system, which can lessen the protection in a crash. Even when children appear to be snugly fitted to their car seats, the coats can introduce slack to the harnessing system.

• As a general rule bulky coats should not be worn underneath the harness because that can leave the harness too loose to be effective in a crash.

Key Car Seat Safety Tips for Cold Weather

Here are actionable steps to follow so you stay within the car seat rules and abide by the car seat crash test ratings (i.e., use the seat how it was tested). This will keep your child warm and safe:

1. Remove the bulky coat before buckling the harness.
   Dress your child in a thin, warm layer (fleece or thermal) that allows the harness to fit snugly against their body.

2. Do the pinch test.
   After buckling the harness, you should not be able to pinch extra webbing at the shoulder. If you can, the straps are too loose, likely because of a coat underneath.

3. Once harnessed, you can cover with a blanket or put the coat back on over the harness.
   Once your child’s harness is properly snug, drape a blanket or coat over the buckled child, and not under the straps.

4. Use coats or covers designed for car seat use.
   If you prefer a coat built for car seats (i.e., designed so the harness goes directly onto the child, then the coat goes over), go with one that states it meets car seat safety guidelines. For example, my friend Dahlia's product, BuckleMeCoats, is designed with car seat compatibility in mind. Dahlia was also on Shark Tank, and I love supporting my friends' small businesses!

5. Warm up the vehicle when possible.
   If you can pre-warm the car, the inside will be more comfortable and this reduces the need for a heavy coat while the child is buckled.

6. Avoid aftermarket inserts or bunting behind the child or under straps.
   Using any padding or bulky layering between the child and harness may alter how the seat performs in a crash. Even if it seems snug now, things compress.

Why It Matters: How the Harness Works

When a crash happens, the car seat is designed to absorb and distribute forces so your child’s body is protected. But if there’s space between the child and the harness (caused by bulky layers), the child can move more than expected, increasing risk of injury or even ejection. The harness needs to be in firm contact with the body. When a heavy coat compresses during a crash, the slack created means the harness doesn’t do its job as intended. The seat is crash-tested with the harness snug against the child’s body, not little pillows of air between them and the straps.

Your Winter Checklist

• Harness tight with no "pinch"-able material? ✔

• Harness at correct height? ✔

• No bulky coat under the straps? ✔

• Installed according to your seat’s manual and vehicle instructions (belt path, angle, tight installation, etc.)? ✔

If you check all these, you’re meeting the car seat guidelines and respecting the car seat requirements and crash test conditions, and this leads to safer travel. 

Follow these car seat safety tips, check the installation, do a regular car seat check, and choose heat-appropriate layers that don’t compromise the harness fit. These simple adjustments go a long way toward safe car rides.

If you ever want a hands-on inspection or personalized guidance, reach out to a Certified Child Passenger Safety Technician (CPST) in your area. Stay warm, stay safe, and buckle up.