Pool opening · State guide
When to Open Your Pool in Hawaii
Last updated: July 15, 2026 · 2 cities covered
Every covered Hawaii city models as year-round: the 7-day mean temperature never drops below the 61°F algae threshold at any of the 2 cities' stations, so there is no forced opening date — or closing deadline anywhere in the state. Each guide below covers the spring refresh routine instead.
Dates in the table are replaced by season length — the number of days with a normal high of 80°F or better — which is the number that actually varies across Hawaii.
| City | Open by | Window opens | 61°F crossing |
|---|---|---|---|
| Honolulu | year-round | 72 swim days | — |
| Kailua | year-round | 231 swim days | — |
Dates are typical-year model outputs, not forecasts — each city guide carries the live widget that tracks the current year against them.
How to use these dates
Each "open by" date is two weeks ahead of that city's own 61°F crossing — the day its 7-day mean temperature (highs and lows averaged, from the nearest NOAA 1991–2020 normals station) reaches the level where unheated pool water starts climbing toward the 65°F algae-growth zone. Opening inside the window means starting up in cold, algae-resistant water: a single label-dosed shock instead of a green-water recovery, and a shopping trip while Hawaii stores are still fully stocked.
Dates are typical-year guidance, not forecasts. A warm or late spring shifts the real-world moment by a week or two in either direction — every city guide carries a live water-temperature widget that tracks the current year against these normals, plus the full 12-step opening checklist sequenced to its local window. New to the process? Start with the generic how-to-open guide and the chemicals shopping list, then come back for your city's dates.