Wait a minute. It's July! In this instance, the culprits for the canyon closure are rockslides produced by extremely heavy precipitation overnight. Apparently Mother Nature wanted to put on her own fireworks show. KSL reports that snowplows are out removing the debris.
Hydrographs along Little Cottonwood Creek show a dramatic spike in streamflow during this period, with a volume exceeding that during the spring runoff.
Thanks to Trevor Alcott for his input on this post.