The weather is still nice and leaves are turning. The nights are cool and can get snow in the upper elevation. Can help with some day hikes, but not the overnight ones. Iceberg lake trail, swiftcurrent pass, grinell glacier all great hikes in the many glacier area.
Many glacier is a great place to hike.
Another great hike is the highline trail at Logan's pass. These are a few hikes. Do not forget to drive the North Fork Road then continue on to Bowman and Kintla lakes. The scenery is spectacular. If you have time consider spending part of the day at two medicine valley or Waterton in Canada.