But one marathoner couldn't see a thing along the route. Kerry Kuck is blind and has Type 1 diabetes, but didn't let either stop him from finishing on the race on Sunday.
"You know when I'm running I'm not blind... it's just a lot of fun," he said.
Kuck has competed in the Half Colfax Marathon for the last five years. This year, he finished the entire marathon with the help of an Iraq war veteran.
"It really was a life changing experience for me to see how inspirational Kerry is to all the runners," his racing partner, David Hagburg said.
They both finished the marathon in about four hours and 50 minutes.
More than 11,000 athletes registered for the marathon, marathon relay, half marathon and Urban 10 Miler.
For more information, visit http://www.coloradocolfaxmarathon.org/
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