The North Face Denali Boys XXS
Got this jacket in sz XXS for my 4 y.o. My son is 38 inches long and 35 lbs. It fits pretty well. So FYI there are the actual measurements of this jacket for sz XXS:
armpit to armpit - 14 1/2"
length (from the middle of the collar to the bottom hem) - 16"
sleeve length from armpit to hem - 10 1/2"
front zipper length - 16 1/2".
Great lightweight but still warm jacket made of wrinkle-free polartec which is kind of water- and windproof.