Phoenix

Phoenix's race calendar splits cleanly along its climate — a dense run of weekly road 5Ks, 10Ks, and half marathons from October through March, once triple-digit summer heat breaks, and a parallel trail and ultra scene that uses the cooler months to push into the desert terrain surrounding the city. South Mountain Park, the largest municipal park in the US at more than 16,000 acres and 58 miles of trail, backs races like the McDowell Mountain Frenzy and Elephant Mountain Trail Runs, while the Black Canyon Ultras push further into the desert. The Phoenix Marathon anchors the road calendar each December, and the Rock 'n' Roll Arizona weekend each January — spanning Tempe, Phoenix, and Scottsdale — draws over 13,000 registered runners, one of the state's largest race weekends.