It is myth that impatiens can't go into your landscape until November or December. Home owners can start early with reasonable care. Plant as early as possible. October is best.
Plant early is our advice.
Another important reason to plant is early is the look you'll have during the holidays. If you expect luxurious robust flowers for Thanksgiving and Christmas, don't wait until the last minute to order your plants. Start early to allow your impatiens to fully establish themselves in your garden. Avoid a possible shortage of quality plants that is a typical problem in November. However, in South and West exposures, all that is required is attention to watering.