USA
Best Time to Dive in Oahu
21.28°N 158.18°W
The best conditions run May to July for the calmest water — seas top 1.5 m on 28% of days, against 63% the rest of the year. The marine life holds steady all year, so the weather picks the month.
- Best time
- May–Jul
- Water
- 25–27 °C
- Visibility
- 25–40 m
- Dived from
- day boat and shore diving
- Tidal range
- 0.4–0.8 m
- Species logged
- 15
Worth knowing: 28% of days see seas over 1.5 m.
Where it is
111 km across · coastline from Natural Earth 10m
Diving in Oahu — monthly breakdown
A year of scuba diving conditions at a glance. Hover a month to isolate it.
| January | February | March | April | May | June | July | August | September | October | November | December | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Conditions | Poor | Poor | Poor | Moderate | Excellent | Excellent | Excellent | Poor | Moderate | Moderate | Moderate | Poor |
| Water temp (°C) | 25 | 25 | 25 | 25 | 26 | 26 | 27 | 27 | 27 | 27 | 27 | 26 |
| Visibility (m) | 30–40 | 30–40 | 30–40 | 30–40 | 30–40 | 30–40 | 30–40 | 30–40 | 30–40 | 30–40 | 30–40 | 25–35 |
| Marine life | Busy | Busy | Busy | Busy | Peak | Peak | Peak | Busy | Busy | Busy | Busy | Busy |
| Best time | Peak | Peak | Peak |
Excellent Good Moderate PoorPeak season May–Jul
Long-term averages, 2016–2025. Visibility is estimated from satellite chlorophyll-a. Water temperature is the surface mean; it is cooler at depth.
The Oahu diving season
April · Shoulder season
1 monthJFMAMJJASOND
- Water temperature
- 25–25 °C
- Visibility
- 30–40 m
- Rain
- 8 days a month
Diving conditionsIt rains more.
May to July · Peak season
3 monthsJFMAMJJASOND
- Water temperature
- 26–27 °C
- Visibility
- 30–40 m
- Rain
- 6 days a month
Diving conditionsThe wind eases.
Marine lifeScalloped hammerhead (likely), Tiger shark (hit-or-miss), Oceanic manta (hit-or-miss) peak at Oahu in these months.
August to November · Shoulder season
4 monthsJFMAMJJASOND
- Water temperature
- 27–27 °C
- Visibility
- 30–40 m
- Rain
- 6 days a month
Diving conditionsSwell is common, and crossings can be rough.
Marine lifeTiger shark (hit-or-miss) peaks at Oahu in these months.
December to March · Off season
4 monthsJFMAMJJASOND
- Water temperature
- 25–26 °C
- Visibility
- 30–40 m
- Rain
- 7 days a month
Diving conditionsThe wind is up.
Marine lifeOceanic manta (hit-or-miss) peaks at Oahu in these months.
- Water temperature is satellite sea-surface temperature, so expect it cooler below the thermocline.
- Visibility is estimated from satellite chlorophyll-a.
Oahu water temperature and weather
4,772 underwater observation records · 29 surveyed years of ocean data · 10 years of sea temperature
Water & weather
Oahu water temperature by month
The dashed line is the monthly average. Eight days in ten fall inside the band.
10th to 90th percentile rangemonthly mean
16
rough days a month
Seas top 1.5 m on 54% of days. Enough to cancel a day boat
0
blowy days a month
Gusts over 40 km/h, about where a day boat stays in port
6
wet days a month
1 of them bring heavy rain
| Month | Swell | Gusts over 40 km/h | Wet days | Heavy rain | Air | Daylight |
|---|---|---|---|---|---|---|
| January | 3.1 m | 1% | 5 | 1 | 27 °C | 10.8 h |
| February | 2.4 m | 3% | 7 | 2 | 26 °C | 11.3 h |
| March | 2.2 m | 2% | 8 | 1 | 27 °C | 11.9 h |
| April | 2.1 m | 1% | 8 | 1 | 28 °C | 12.5 h |
| May | 1.9 m | 0% | 9 | 1 | 28 °C | 13.0 h |
| June | 1.7 m | 0% | 5 | 0 | 30 °C | 13.3 h |
| July | 1.6 m | 0% | 4 | 0 | 31 °C | 13.2 h |
| August | 1.7 m | 0% | 6 | 0 | 31 °C | 12.7 h |
| September | 1.5 m | 1% | 7 | 0 | 31 °C | 12.1 h |
| October | 2.0 m | 1% | 8 | 0 | 30 °C | 11.5 h |
| November | 2.4 m | 4% | 4 | 0 | 29 °C | 11.0 h |
| December | 2.9 m | 2% | 6 | 2 | 27 °C | 10.7 h |
Swell is the rough end of the month: nine days in ten come in under it. Sea temperature covers 10 years, waves 4.
Pick your week
48 weeks from the daily record. Darker is better, against this site's own year. Pick a month for the detail.
| Week 1 | January week 1: Poor | February week 1: Poor | March week 1: Poor | April week 1: Poor | May week 1: Excellent | June week 1: Excellent | July week 1: Excellent | August week 1: Poor | September week 1: Moderate | October week 1: Good | November week 1: Good | December week 1: Moderate |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Week 2 | January week 2: Poor | February week 2: Poor | March week 2: Poor | April week 2: Poor | May week 2: Good | June week 2: Excellent | July week 2: Excellent | August week 2: Poor | September week 2: Moderate | October week 2: Moderate | November week 2: Good | December week 2: Poor |
| Week 3 | January week 3: Poor | February week 3: Poor | March week 3: Moderate | April week 3: Good | May week 3: Good | June week 3: Excellent | July week 3: Excellent | August week 3: Poor | September week 3: Poor | October week 3: Poor | November week 3: Poor | December week 3: Poor |
| Week 4 | January week 4: Poor | February week 4: Poor | March week 4: Moderate | April week 4: Good | May week 4: Excellent | June week 4: Excellent | July week 4: Excellent | August week 4: Poor | September week 4: Poor | October week 4: Good | November week 4: Poor | December week 4: Poor |
Excellent Good Moderate PoorBest week to go: fourth of May
January, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 25 °C | 2.9 m | 20 km/h | 14% |
| Week 2 | Poor | 25 °C | 3.2 m | 18 km/h | 13% |
| Week 3 | Poor | 25 °C | 3.1 m | 19 km/h | 16% |
| Week 4 | Poor | 25 °C | 2.8 m | 21 km/h | 23% |
February, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 25 °C | 2.6 m | 22 km/h | 25% |
| Week 2 | Poor | 25 °C | 2.3 m | 21 km/h | 28% |
| Week 3 | Poor | 25 °C | 2.3 m | 21 km/h | 28% |
| Week 4 | Poor | 25 °C | 2.3 m | 24 km/h | 24% |
March, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 25 °C | 2.4 m | 26 km/h | 22% |
| Week 2 | Poor | 25 °C | 2.3 m | 23 km/h | 25% |
| Week 3 | Moderate | 25 °C | 2.2 m | 21 km/h | 27% |
| Week 4 | Moderate | 25 °C | 2.1 m | 22 km/h | 27% |
April, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 25 °C | 2.3 m | 23 km/h | 28% |
| Week 2 | Poor | 25 °C | 2.3 m | 24 km/h | 27% |
| Week 3 | Good | 25 °C | 2.0 m | 25 km/h | 26% |
| Week 4 | Good | 25 °C | 2.0 m | 24 km/h | 29% |
May, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 25 °C | 2.0 m | 24 km/h | 27% |
| Week 2 | Good | 25 °C | 2.0 m | 24 km/h | 30% |
| Week 3 | Good | 26 °C | 1.9 m | 23 km/h | 35% |
| Week 4 | Excellent | 26 °C | 1.6 m | 22 km/h | 24% |
June, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 26 °C | 1.7 m | 23 km/h | 15% |
| Week 2 | Excellent | 26 °C | 1.6 m | 24 km/h | 14% |
| Week 3 | Excellent | 26 °C | 1.6 m | 24 km/h | 18% |
| Week 4 | Excellent | 26 °C | 1.7 m | 23 km/h | 17% |
July, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 27 °C | 1.6 m | 24 km/h | 13% |
| Week 2 | Excellent | 27 °C | 1.6 m | 25 km/h | 11% |
| Week 3 | Excellent | 27 °C | 1.7 m | 25 km/h | 11% |
| Week 4 | Excellent | 27 °C | 1.6 m | 26 km/h | 11% |
August, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 27 °C | 1.8 m | 26 km/h | 12% |
| Week 2 | Poor | 27 °C | 1.8 m | 24 km/h | 15% |
| Week 3 | Poor | 27 °C | 1.6 m | 23 km/h | 19% |
| Week 4 | Poor | 27 °C | 1.6 m | 23 km/h | 22% |
September, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Moderate | 27 °C | 1.5 m | 22 km/h | 20% |
| Week 2 | Moderate | 27 °C | 1.5 m | 22 km/h | 20% |
| Week 3 | Poor | 27 °C | 1.5 m | 23 km/h | 24% |
| Week 4 | Poor | 27 °C | 1.6 m | 23 km/h | 24% |
October, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Good | 28 °C | 1.8 m | 21 km/h | 25% |
| Week 2 | Moderate | 27 °C | 2.1 m | 20 km/h | 26% |
| Week 3 | Poor | 27 °C | 2.3 m | 21 km/h | 25% |
| Week 4 | Good | 27 °C | 2.0 m | 21 km/h | 22% |
November, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Good | 27 °C | 2.0 m | 21 km/h | 16% |
| Week 2 | Good | 27 °C | 2.1 m | 23 km/h | 12% |
| Week 3 | Poor | 27 °C | 2.4 m | 23 km/h | 11% |
| Week 4 | Poor | 26 °C | 2.7 m | 22 km/h | 13% |
December, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Moderate | 26 °C | 2.7 m | 20 km/h | 19% |
| Week 2 | Poor | 26 °C | 2.7 m | 22 km/h | 21% |
| Week 3 | Poor | 26 °C | 3.1 m | 24 km/h | 18% |
| Week 4 | Poor | 25 °C | 3.0 m | 22 km/h | 15% |
10 years of daily records, averaged into weeks.
Gear & storms
What to wear
Off the coldest water of each month, not the average — that is what the suit has to cope with.
| January | February | March | April | May | June | July | August | September | October | November | December | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Suit | January: 3 mm | February: 5 mm | March: 5 mm | April: 3 mm | May: 3 mm | June: 3 mm | July: 3 mm | August: 3 mm | September: 3 mm | October: 3 mm | November: 3 mm | December: 3 mm |
- Apr–Jan3 mm full suit
- Feb–Mar5 mm full suit
Swell through the year
The rough end of each month — nine days in ten come in under it.
Amber is over 1.5 m.
Tides
Tropical storms
3 of the last 30 Augusts saw a tropical storm pass within 250 km. Anything has been recorded Jul–Oct.
Share of the last 30 years with a storm that month.
- NOAASea surface temperature, from OISST and MUR
- ERA5Wind, waves, rain and air temperature, via Open-Meteo
- OBISMarine species records within 60 km
- IBTrACSTropical cyclone tracks, 1996 to 2025
Oahu marine life — what you'll see diving
| Species | When | Observed window | Reliability | Evidence | Records |
|---|---|---|---|---|---|
| Green turtle | All year | Near-guaranteed | 2258 | ||
| Spinner dolphin | All year | Near-guaranteed | 142 | ||
| Humpback whale | Feb–Mar | Near-guaranteed | 1719 | ||
| Whitetip reef shark | All year | Near-guaranteed | 228 | ||
| Ocellated eagle ray | All year | Likely | 156 | ||
| Bottlenose dolphin | All year | Likely | 38 | ||
| Scalloped hammerhead | May–Jul | Likely | 32 | ||
| Reef manta | All year | Likely | 31 | ||
| Tiger shark | Jun–Sep | Hit-or-miss | 18 | ||
| Short-finned pilot whale | May, Oct–Nov | Likely | 63 | ||
| Spotted eagle ray | Jun, Oct–Dec | Hit-or-miss | 23 | ||
| Bigeye trevally | Feb, Oct–Nov | Hit-or-miss | 14 | ||
| Hawksbill turtle | Jan, May, Jul, Sep | Likely | 12 | ||
| Blacktip reef shark | Mar, Jun–Jul | Hit-or-miss | 11 | ||
| Oceanic manta | Feb, Jul | Hit-or-miss | 10 |
Peak Present
- Observed window
- Months with records. Peak is where most of them fall.
- Reliability
- Near-guaranteed in 60% of surveyed years or more
- Likely 30% to 60%
- Hit-or-miss under 30%
- Evidence
- Years it was seen, out of the years anyone surveyed.
- Records
- OBIS sightings within 60 km.
These are sightings people logged, not a full survey of the reef. A species missing from a month may just mean nobody recorded one.
Diving Oahu — common questions
- When is the best time to dive Oahu?
- The best conditions run May to July for the calmest water — seas top 1.5 m on 28% of days, against 63% the rest of the year. The marine life holds steady all year, so the weather picks the month.
- When is the diving season in Oahu?
- The diving season in Oahu runs May to July.
- Is the diving in Oahu good for beginners?
- Yes. It suits Open Water divers, so it works for a first trip after certification.
- How warm is the water in Oahu?
- Between 25 and 27 °C at the surface across the year, coldest in February and warmest in September. It runs cooler below the thermocline.
- What wetsuit do I need in Oahu?
- A 5 mm full suit covers the coldest water of the year. In the warmest months a 3 mm full suit is enough.
- What is the visibility like in Oahu?
- Roughly 25 to 40 m depending on the month. That is estimated from satellite chlorophyll-a rather than measured in the water.
- What will I see diving Oahu?
- The most consistently recorded species are Green turtle (near-guaranteed), Spinner dolphin (near-guaranteed) and Humpback whale (near-guaranteed), from 4,772 records within 60 km.
- Does Oahu get tropical storms?
- Yes. Over 30 years of records a storm passed within 250 km in Jul–Oct, most often in August at 3 of 30 years.
- Is there current in Oahu?
- The tide rises and falls 0.8 m around the full and new moon, against 0.4 m in between. How much of that becomes current depends on the shape of the channel.
- When should I avoid Oahu?
- December–February are the weakest months for conditions.
- How do you dive Oahu?
- Mostly from day boats and the shore. Trips run through the season, May–Jul.