this is a cute jacket for temps in the 60s and 50s. it is not super thick or windproof, so it really isn't great for cooler fall days.  it also runs quite small - my son wears 3T in everything and the 3T in this jacket is really too snug for him.  it fits fine over a teeshirt - but since it is a lightweight jacket, i have wanted to layer it over a sweater & i have found that it was really too small to do this.  i strongly suggest ordering a size up so you get more use out of it - both by being able to layer and by having it last more than one season.