At least one waterpark will be opened every day of the year. In the winter months, there is a trade-off where one waterpark will be open, the other closed for rehab. Once the rehab is done, they switch, the other one closes and the other re-opens.
usually in December they are both closed for two weeks each for refurbishment. but the two park closure is not at the same time, one closes the first two week the other is the second half of the month.