Just find a strain with a finish date in October for Amsterdam and you'll be OK. First frost here is abouts October 1st, because we are so much farther south than Amsterdam our finish date is about a month earlier than theirs. Check for the outside finish date on strains, if they don't have it than assume the strain is an indoor variety that you don't want. Indoor varieties are like poodles, pampered and inbreed, outdoor growers want a tough hardy strain that can survive on its own.