Parents know the drill — hats, mittens, and a big winter coat before heading out the door. But what if the same coat that keeps them warm could also put your child at risk in the car? Consumer Reports explains how to keep little ones both safe and snug all season long.

In colder weather, it’s normal for parents to want to bundle up their children, but thick puffy coats and car seat harnesses don’t work well together.

Emily Thomas is an expert in auto safety with Consumer Reports. But even more importantly she’s a mom of two boys. Emily says, “I totally understand the inconvenience of having to be like, okay, now you're at the car, you’ve got to take your coat off so I can put you into your car seat. But it does matter.”

That’s because thick winter coats can create extra space between a child and their harness straps — space that disappears in a crash, leaving your child at risk. The additional room can increase movement outside the protection of their car seat. It increases the risk of injury.

To check if a coat is too bulky, buckle your child in with it on and tighten the straps. Check at their shoulders. Make sure that you can’t pinch any webbing between your fingers. Make sure the chest clip is at armpit level.

Then take them out, remove the coat, and buckle them in again without adjusting the harness.

Now when you go to check that harness at their shoulders, if you can pinch any webbing between your fingers, that means that that coat has now introduced some slack into the system, and it’s creating an unsafe environment for your child.

The safest way to keep kids warm is simple: buckle them in first, then cover them with a blanket or coat on top. And for older kids, you can have them wear their coat on backwards on top of their harness.

When it comes to winter travel, a few extra seconds can make all the difference in keeping your child safe. You never know when a crash is going to happen, so you have to be prepared for every single ride.

Consumer Reports also recommends attending a car-seat checkup event periodically to ensure your child’s seat is installed correctly.