Oahu records about 460mm of rain across roughly 100 wet days a year, which is a 27% chance on an average day. December is the wettest month at 68mm (15% of the annual total) and June the driest at 15mm. Local rain type: brief showers. Waikiki and the south shore are dry 90% of the time. The Ko'olau Mountains and windward coast see frequent showers. Trade wind showers rarely last more than 15 minutes and produce spectacular rainbows.
Chance of rain on an average day: 27%
Rainfall climatology for Oahu. The live hour-by-hour answer for today loads at the top of this page from Open-Meteo and refreshes through the day — the figures below describe a typical year, not today.
Conditions on this page are recalculated from the latest forecast every time it is opened, for the current date in the location's own time zone. Showing .
| Annual rainfall | 460mm |
| Rain days per year | 100 |
| Odds on an average day | 27% |
| Wettest month | December — 68mm over 14 days |
| Driest month | June — 15mm over 3 days |
| Rain type | brief showers |
| Best dry window | May through September is the driest period with reliable sunset conditions for North Shore and west coast photography. |
| Worst rain window | January brings the heaviest rains — the North Shore sees massive winter swells and occasional flooding in low-lying areas. |
December delivers 353% more rain than June (68mm vs 15mm). That gap is the difference between planning around showers and ignoring them.
No single month holds more than 15% of the annual total, so rain in Oahu is spread through the year — there is no season you can rely on being dry.
Oahu rain typically comes as discrete showers, so a compact umbrella and a flexible plan are usually enough.
Rain falls on about 14 days in December against 3 in June — the frequency swing matters more for planning than the millimetre totals.
Climate normals. Use them to judge whether today's live forecast at the top of the page is typical or unusual for the season.
| Month | Rainfall | Rain days | Chance on a given day | Highs |
|---|---|---|---|---|
| January | 65mm | 14 | 47% | 27°C |
| February | 55mm | 12 | 40% | 27°C |
| March | 50mm | 10 | 33% | 28°C |
| April | 30mm | 6 | 20% | 28°C |
| May | 25mm | 5 | 17% | 30°C |
| June | 15mm | 3 | 10% | 30°C |
| July | 18mm | 4 | 13% | 31°C |
| August | 20mm | 4 | 13% | 31°C |
| September | 28mm | 6 | 20% | 30°C |
| October | 45mm | 9 | 30% | 30°C |
| November | 58mm | 12 | 40% | 28°C |
| December | 68mm | 14 | 47% | 28°C |
Rain probability is the chance that at least 0.2mm falls at your location — not how long it rains. For Oahu we combine the hourly probability curve, expected volume in millimetres, and the city's own rainfall record into a single umbrella verdict.
| Factor | Weight | What it measures |
|---|---|---|
| Hourly probability | 40% | Peak and sustained chance of measurable rain across the next 24 hours. |
| Expected volume | 30% | Total millimetres, which separates a passing shower from a genuine soaking. |
| Timing & duration | 20% | When rain starts, when it eases, and the longest continuous dry window. |
| Local rain type | 10% | Drizzle, brief showers, thunderstorms or monsoon — each needs different gear. |
Live hourly values come from Open-Meteo and refresh through the day. Monthly rainfall figures are climate normals, so they describe a typical year rather than a forecast.
Oahu records rain on roughly 100 days a year — about a 27% chance on any given day — totalling around 460mm.
December, with about 68mm over 14 rain days. That is 15% of the entire year's rainfall in a single month.
June is the driest month at 15mm across roughly 3 days. May through September is the driest period with reliable sunset conditions for North Shore and west coast photography.
Waikiki and the south shore are dry 90% of the time. The Ko'olau Mountains and windward coast see frequent showers. Trade wind showers rarely last more than 15 minutes and produce spectacular rainbows.
No. Probability is the chance that at least 0.2mm of rain falls at your location at some point in the period. Check the expected millimetres alongside it: 40% with 0.4mm is a passing shower, 40% with 12mm is a soaking.