For Karen and anyone else from warmer climes, Alaska will probably feel cold to you anyway, September or not. Every year is different, so our experience will not necessarily match yours, but our first AK trip was that same week in SEpt. They had had an early frost, and fall colors had started inland,north of Anchorage. We found temperatures comfortable (for those of us who are used to cold weather), namely highs between 50 and 60, lows around 40 overnight. Sunshine was abundant the week we were there (not always true) so we were comfortable in jeans, longsleeved shirts and quilted vests or sweatshirts. It could also be warmer than that this year - probably not much colder, though perhaps a bit raw if it's rainy and damp. Layers, layers, layers - that's the word on clothes. If the idea of the dogsled ride appeals to you, then layer up and enjoy!