A few things

Our wedding is occurring  in the Colorado Rocky Mountains, at an altitude of 11,550 feet (3,520 m) above sea level. As such there are a few  atypical things to consider. 

Altitude:

25 to 30% of people  get altitude sickness. Symptoms include: headache, nausea, fatigue and trouble sleeping due to a lack of available oxygen. Nose bleeds may occur too even if you’ve never had one (at/near sea level). Typically it takes 1-2 days  to acclimatise. Plenty of water and rest are critical. Regular pain killers  can help with headaches. Just as in an aircraft, alcohol has more impact at altitude.

 Denver is ~  half way up, so  an overnight there may reduce  altitude sickness.  https://www.denverpost.com/2016/11/23/altitude-sickness-tips-colorado/

Weather/Fire:

Snow/hail/high winds and lashings of ginger beer are all possible  in mid-summer. Thunderstorms (spectacular but deadly) are a very serious danger during summer afternoons. 

The high altitude that removes all the atmospheric oxygen also ramps up the UV. Hats, sunglasses and body coverage (clothes and/or lotions) are all advised i.e. “slip, slap, slop” to quote the Australians.

Summer is fire season. Obey all fire warnings and restrictions.