I can't tell you about Colorados weather, but I can tell you that the rut happens the same every year. The peak activity times of the day may vary from year to year, depending on the weather conditions. Elk rut is determined by the amount of daylight decreasing. The change in sunlight will increase testosterone levels and cause the velvet to harden and the bulls to start feeling their oats so to speak. The same goes for the cows and estrogen levels.

In areas with older populations of cows, you will find that the activity level will pick up earlier in the season, as the older cows will cycle earlier than the younger cows. Where i hunt at, it is not uncommon to hear a bunch of bugling in August as there are a couple of hot cows running amuck already.

The most activity in the rut is usually around the 3rd week of september, that is when most like to be out there, however I have seen years where this was the quietest week during the daylight hours because of ungodly temperatures making the elk do their work at the coolest times of the day, which would be at night. Even though things may be quiet during the day, does not mean that the rut isn't happening. The key to success in other than normal circumstances, is knowing what adjustments to make when mother nature throws you a curve ball. Good luck