Both of my kids were faster-than-normal growers. They both (one boy, one girl, 4 years apart in age) wore size 2T at 12 months of age, were in 3T by 18 months, 4T by 24 months.....etc. Neither slowed down until about age 3/4 years. Now DS is 10 years old, wears size 12/14 with size 10 men's shoe! DD is 6 years old and is wearing size 7/8 and hovering between a size 2/3 shoe. I learned very quickly with my 2 to never buy clothes ahead as it wouldn't do me any good (although my Dad once bought my DS a size 12 month cute Pooh outfit when DS was born thinking it would be cute on him when he was a year old.....DS wore it to get his 6 month pictures in.....and it barely still fit! LOL). If I were you, I'd wait a bit and see if she has another growth spurt before cold weather sets in. Or just buy a few things in 2T and 3T so you'll have something in both to have on hand without too much in either if it ends up not being the size you need.