Why that window
Two clocks run in spring. The comfort clock: once daily averages pass the low-to-mid 60s°F, water reaches genuinely swimmable temperature within a couple of weeks. The algae clock: a covered pool warms faster than an open one, and somewhere in the 50s°F water range algae wakes up under that cover with no chlorine to stop it. Opening inside — or slightly ahead of — your city's window satisfies both: you're circulating and sanitizing before algae hits stride, and swimming arrives on schedule.
Opening day, in order
Pull and clean the cover, top up water, reconnect the equipment, and get the pump turning over. Then test everything — chlorine, pH, alkalinity, stabilizer, calcium — and correct in that order. The dosing calculator turns your first reading of the year into exact amounts in cups and pounds, and the volume calculator nails down the gallon figure every dose depends on.
Frequently asked questions
Do Hawaii pools ever open for the season?
In Honolulu and Hilo, there's no real opening day — daily averages stay above 65°F in every month, so pools run year-round. The seasonal rhythm is lighter care in the cooler months, not a cover.
Why do the dates differ across Hawaii?
Because each city's dates come from its own NOAA 1991–2020 station records, and geography does the rest — elevation, latitude, coastlines, and urban heat spread the same milestone across weeks. That local spread is exactly what a national "open on Memorial Day" rule misses.