Good advice on heading up in the morning. You never know what the afternoon weather will be (don't use the Denver forecast) these mountains create their own weather. Bring a warm jacket in the saddle bag. Watch out for the goats. Spend the night in Denver or a higher altitude before you go up. I live at 7500 ft, and I have been up there and many of the passes in Colorado. I'm used it , but have seen several get altitude sickness, just drink lots of water, more than you think you need, and you will be fine.

 

Got snowed on in July near Summit lake a couple yrs ago. Bring a jacket.

 

Here's a good video of the ride. Don't know how long this couple stayed on top but watch how the weather changed on them during the trip.

 

Nice video Whiskers. Nicely edited. Recommend doing that trip early in the day as was previously stated. Also watch for gravel at the Chicago Creek Campground turnoff.
Another great ride is Trail Ridge Road. The highest continuous paved road.