Flew from Denver to SALT Lake Oct. 17th. All the high lakes I saw were still open. That being said, virtually any lake at 12,000 ft will be frozen by Halloween. Most of the 10,000 ft lakes take till Veterans day. Of course there are exceptions to every rule. My earliest ice fishing was Nov. 4th and my latest was June 10th.
Iced Lake John on Nov. 10th one year. Only one little corner but it was ice fishing. Used a tire iron to cut holes.
Iced 11-mile Nov. 20th. One year couldnt get on till Dec.10th.
Iced Antero Nov. 15th.
Good luck.