This is a nice thread to reread at this time of year. I didn't realize that Ennis visited the Twist house in October.
Front-Ranger, I think the month is more likely to be November or even December but it's impossible to be definitive about this.
What we do know is that Ennis had sent Jack a postcard suggesting a reunion at Pine Creek on November 7 and that this postcard was returned to Ennis stamped "deceased". What we don't know is how far ahead of November 7 the "deceased" postcard got to Ennis though it could have been only a matter of days before his departure for the reunion. Ennis then phones Lureen to find out what has happened and it's during this conversation that she suggests that Ennis visit the Twists and work out what should be done with the remaining half of Jack's ashes.
Some time, obviously, has to elapse between this phone call and the date that Ennis sets out to visit the Twists but again we don't know how long this is.
All in all, however, I find it more likely that Ennis visited the Twists in November - or even December - rather than October.
Somehow, psychologically, emotionally, artistically - whatever - I find the bleaker days of November or December a more appropriate backdrop for this scene rather than the warmer and more colourful days of October.