The weather is definetly beginning to change. Yes, the days are getting shorter and the darkness is falling upon us earlier in the evenings. The smells and sights of fall and approaching winter are all around.
The air is beginning to feel cooler, and the days when the the sun is shining are not as warm as they once were. The beauty of the changing colors is beginning to appear. The leaves are starting to turn, especially in the higher elevations. This is a great time to take a drive or a motorcycle ride through the mountains.
Of course, if you want to take a break from the colder temperatures (at least during the day), you could go to the Valley of Fire State Park near Las Vegas.
This place stays pretty warm during the daytime, even in the fall and parts of the winter. Since it is in the desert, however, the nights can get pretty cold. If you are thinking about camping in the Valley of Fire State Park this fall or winter, make sure you have a really, really warm sleeping bag, and cold weather clothing.
You can find more about Valley of Fire State Park at this site.