Universal has confirmed Volcano Bay enters seasonal closure on October 26, which makes Sunday October 25 the last day to get in.
The park is scheduled to reopen on or before March 24, 2027 — a roughly five-month shutdown for refurbishment and infrastructure work, one of the longest in its history. Universal has already suspended sales and renewals of 3-Park Annual Passes that include Volcano Bay access.
If a water park day is part of your fall I-Drive plan, this is a hard deadline.