I got this in size 12 months for my daughter turning 1 in December in Wisconsin. She wore it all winter with no problem with either size or warmth. Some people have criticized this suit in other reviews for being too thin and therefore not warm enough for cold weather, but I disagree completely. She was plenty warm even in short bouts of below zero temps. At first look it does seem thin compared to a lot of winter coats made for kids, but it did the job for us. And if we were just running errands, I usually didn't even need a hat or mittens underneath - just use the hood and the fold-over sleeves! It was also GREAT for being in the car seat since there's no extra bulk to make safety an issue. If we planned to be outside for an extended period of time, I made sure she was wearing thicker clothing underneath, but not much extra besides regular clothing. In fact, if I put too much more than that underneath she was all sweaty when we got inside! I plan to buy another one this year in 24 months because it was so great! Awesome buy in my opinion. I had a friend who bought the next thicker Columbia bunting and she rarely used it because her little one was too warm in it most of the time; this one is just right!