Every year, Disney closes each of the water parks located in Disney World for an annual refurbishment. This is to carry basic maintenance throughout the water parks; as you can imagine these parks are much more difficult to maintain and require special attention. Usually, Blizzard Beach closes for a couple of weeks in the fall and reopens before the holidays. Then at that point, Typhoon Lagoon closes at the start of winter and usually reopens in early spring. Things will be a little different this year.
Blizzard Beach is currently scheduled to close on September 8th, 2019. It is currently scheduled to reopen on January 5th, 2020. This means the closure period for Blizzard Beach will be several weeks longer than usual. There are rumors that Blizzard Beach will get some enhancements, like Typhoon Lagoon has received in the last couple of years, but there is no official word for Disney yet. Typhoon Lagoon will remain open throughout this period and will close for its annual refurbishment on January 5th, 2020.