It fit my little man at 2-3 months...but he is a BIG baby! at 4 months he was already weighing in at 18lbs. Its not a thick material though so you could put it on at any time of year. Hope that helps :)
Thank you..that info helps! And for those of you confused by my question I was SUPPOSED to be typing 'fit"..not implying her baby was a fighter at 3 months.LOL