B.B.
BABYLEGS!!! They are baby legwarmers that you can put under clothes, but you still have easy access for diaper changes. Good for boys and girls! We're in TX, and right now it's starting to get chili in the mornings, so my little guy wears these in place of pants, since they're easy to remove for later when it warms up. But when it gets cold both my boys (3 years and 10 months) will wear them under their pants. They're also great for crawlers so their knees don't get all red. Makes for easy diaper changes. And they're super cute!!
www.babylegs.com is the website, but you can also just cut the feet off of knee high socks. If you want, you can sew a hem at the bottom. But I don't sew, so I don't, and they don't fray.
Layers are best. That way if you're inside you can remove the warmest layers if needed.