According to official Dota 2 blog, todays patch adds in a summer update to Dota Plus which focuses on making improvements to some existing features, while also adding in some all new things for all Dota Plus subscribers.
These all-new features include a new Summer Terrain, support for Turbo Mode, and dozens of new Plus Hero Challenges. To learn more about the new features coming to Dota 2 with the Dota Plus Summer Update, check out the patch notes.
Source: N4G PC Dota Plus Summer Update Now Available