USA
Best Time to Dive in Kauai / Niihau
21.87°N 160.10°W
Closed October to April. Divers come for Niihau's clear summer water, lava tubes and monk seals. That does not change through the year, so go when the weather is best: August to September.
- Best time
- Aug–Sep
- Water
- 25–28 °C
- Visibility
- 20–35 m
- Dived from
- day boat
- Tidal range
- 0.4–0.8 m
- Species logged
- 7
Worth knowing: 42% of days see seas over 1.5 m.
Where it is
111 km across · coastline from Natural Earth 10m
Diving in Kauai / Niihau — 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 | Closed | Closed | Closed | Closed | Poor | Excellent | Excellent | Excellent | Poor | Closed | Closed | Closed |
| Water temp (°C) | 25 | 25 | 25 | 25 | 26 | 26 | 27 | 27 | 28 | 27 | 27 | 26 |
| Visibility (m) | 25–35 | 20–30 | 25–35 | 25–35 | 25–35 | 25–35 | 25–35 | 20–30 | 25–35 | 25–35 | 25–35 | 20–30 |
| Marine life | Closed | Closed | Closed | Closed | Steady | Busy | Steady | Busy | Steady | Closed | Closed | Closed |
| Best time | Peak | Peak |
Excellent Good Moderate PoorPeak season Aug–Sep
Long-term averages, 2016–2025. Visibility is estimated from satellite chlorophyll-a. Water temperature is the surface mean; it is cooler at depth.
The Kauai / Niihau diving season
May to September · Peak season
5 monthsJFMAMJJASOND
- Water temperature
- 26–28 °C
- Visibility
- 25–35 m
- Rain
- 15 days a month
Diving conditionsSwell is common, and crossings can be rough. The wind eases. It rains more.
October to April · Closed
7 monthsJFMAMJJASOND
The site is closed to diving in these months.
- Water temperature is satellite sea-surface temperature, so expect it cooler below the thermocline.
- Visibility is estimated from satellite chlorophyll-a.
Kauai / Niihau water temperature and weather
8,419 underwater observation records · 23 surveyed years of ocean data · 10 years of sea temperature
Water & weather
Kauai / Niihau 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
20
rough days a month
Seas top 1.5 m on 68% 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
13
wet days a month
1 of them bring heavy rain
| Month | Swell | Gusts over 40 km/h | Wet days | Heavy rain | Air | Daylight |
|---|---|---|---|---|---|---|
| January | 3.5 m | 5% | 8 | 1 | 26 °C | 10.8 h |
| February | 2.7 m | 5% | 10 | 1 | 25 °C | 11.3 h |
| March | 2.5 m | 4% | 12 | 2 | 25 °C | 11.8 h |
| April | 2.5 m | 0% | 14 | 1 | 26 °C | 12.5 h |
| May | 2.1 m | 0% | 16 | 1 | 27 °C | 13.0 h |
| June | 1.8 m | 0% | 15 | 1 | 28 °C | 13.3 h |
| July | 1.7 m | 1% | 14 | 0 | 29 °C | 13.2 h |
| August | 1.8 m | 0% | 15 | 0 | 29 °C | 12.8 h |
| September | 1.7 m | 0% | 15 | 0 | 29 °C | 12.1 h |
| October | 2.2 m | 0% | 16 | 1 | 28 °C | 11.5 h |
| November | 2.7 m | 2% | 9 | 1 | 27 °C | 10.9 h |
| December | 3.2 m | 2% | 10 | 1 | 26 °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: Poor | June week 1: Excellent | July week 1: Excellent | August week 1: Excellent | September week 1: Poor | October week 1: Poor | November week 1: Poor | December week 1: Poor |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Week 2 | January week 2: Poor | February week 2: Poor | March week 2: Poor | April week 2: Poor | May week 2: Poor | June week 2: Good | July week 2: Excellent | August week 2: Excellent | September week 2: Moderate | October week 2: Poor | November week 2: Poor | December week 2: Poor |
| Week 3 | January week 3: Poor | February week 3: Poor | March week 3: Poor | April week 3: Poor | May week 3: Moderate | June week 3: Excellent | July week 3: Good | August week 3: Good | September week 3: Moderate | 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: Poor | April week 4: Poor | May week 4: Moderate | June week 4: Excellent | July week 4: Excellent | August week 4: Good | September week 4: Moderate | October week 4: Poor | November week 4: Poor | December week 4: Poor |
Excellent Good Moderate PoorBest week to go: first of August
January, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 25 °C | 3.3 m | 22 km/h | 22% |
| Week 2 | Poor | 25 °C | 3.7 m | 20 km/h | 25% |
| Week 3 | Poor | 25 °C | 3.5 m | 20 km/h | 29% |
| Week 4 | Poor | 25 °C | 3.2 m | 23 km/h | 31% |
February, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 25 °C | 3.0 m | 24 km/h | 30% |
| Week 2 | Poor | 25 °C | 2.7 m | 24 km/h | 35% |
| Week 3 | Poor | 25 °C | 2.7 m | 25 km/h | 40% |
| Week 4 | Poor | 25 °C | 2.7 m | 25 km/h | 38% |
March, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 24 °C | 2.7 m | 25 km/h | 37% |
| Week 2 | Poor | 24 °C | 2.5 m | 25 km/h | 35% |
| Week 3 | Poor | 25 °C | 2.4 m | 23 km/h | 37% |
| Week 4 | Poor | 25 °C | 2.4 m | 22 km/h | 43% |
April, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 25 °C | 2.5 m | 22 km/h | 48% |
| Week 2 | Poor | 25 °C | 2.5 m | 23 km/h | 49% |
| Week 3 | Poor | 25 °C | 2.2 m | 22 km/h | 49% |
| Week 4 | Poor | 25 °C | 2.1 m | 22 km/h | 50% |
May, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 25 °C | 2.1 m | 22 km/h | 53% |
| Week 2 | Poor | 25 °C | 2.1 m | 22 km/h | 51% |
| Week 3 | Moderate | 26 °C | 2.0 m | 20 km/h | 48% |
| Week 4 | Moderate | 26 °C | 1.8 m | 18 km/h | 49% |
June, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 26 °C | 1.8 m | 18 km/h | 50% |
| Week 2 | Good | 26 °C | 1.7 m | 19 km/h | 48% |
| Week 3 | Excellent | 26 °C | 1.8 m | 18 km/h | 54% |
| Week 4 | Excellent | 27 °C | 1.8 m | 18 km/h | 54% |
July, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 27 °C | 1.8 m | 18 km/h | 46% |
| Week 2 | Excellent | 27 °C | 1.8 m | 18 km/h | 44% |
| Week 3 | Good | 27 °C | 1.7 m | 19 km/h | 47% |
| Week 4 | Excellent | 27 °C | 1.7 m | 19 km/h | 44% |
August, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 27 °C | 1.9 m | 19 km/h | 40% |
| Week 2 | Excellent | 27 °C | 1.8 m | 18 km/h | 49% |
| Week 3 | Good | 27 °C | 1.7 m | 18 km/h | 53% |
| Week 4 | Good | 28 °C | 1.8 m | 18 km/h | 53% |
September, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 28 °C | 1.7 m | 18 km/h | 53% |
| Week 2 | Moderate | 28 °C | 1.6 m | 18 km/h | 50% |
| Week 3 | Moderate | 28 °C | 1.7 m | 18 km/h | 48% |
| Week 4 | Moderate | 28 °C | 1.7 m | 18 km/h | 51% |
October, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 28 °C | 1.9 m | 18 km/h | 55% |
| Week 2 | Poor | 27 °C | 2.2 m | 19 km/h | 53% |
| Week 3 | Poor | 27 °C | 2.4 m | 20 km/h | 50% |
| Week 4 | Poor | 27 °C | 2.3 m | 19 km/h | 52% |
November, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 27 °C | 2.3 m | 20 km/h | 45% |
| Week 2 | Poor | 27 °C | 2.4 m | 21 km/h | 31% |
| Week 3 | Poor | 27 °C | 2.7 m | 22 km/h | 25% |
| Week 4 | Poor | 26 °C | 3.1 m | 23 km/h | 26% |
December, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 26 °C | 3.0 m | 22 km/h | 32% |
| Week 2 | Poor | 26 °C | 2.9 m | 23 km/h | 31% |
| Week 3 | Poor | 26 °C | 3.5 m | 23 km/h | 32% |
| Week 4 | Poor | 25 °C | 3.3 m | 23 km/h | 29% |
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: skin | October: 3 mm | November: 3 mm | December: 3 mm |
- Oct–Jan3 mm full suit
- Feb–Mar5 mm full suit
- Apr–Aug3 mm full suit
- Sepskin or 3 mm shorty
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
1 of the last 30 Julys 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
Kauai / Niihau marine life — what you'll see diving
| Species | When | Observed window | Reliability | Evidence | Records |
|---|---|---|---|---|---|
| Humpback whale | Feb | Near-guaranteed | 318 | ||
| Spinner dolphin | All year | Near-guaranteed | 79 | ||
| Green turtle | All year | Near-guaranteed | 80 | ||
| Minke whale | Feb–Apr | Hit-or-miss | 7692 | ||
| Bryde's whale | Sep–Oct | Hit-or-miss | 168 | ||
| Bottlenose dolphin | Feb, Jun, Aug | Likely | 39 | ||
| Short-finned pilot whale | Feb, Jun | Likely | 19 |
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 Kauai / Niihau — common questions
- When is the best time to dive Kauai / Niihau?
- Closed October to April. Divers come for Niihau's clear summer water, lava tubes and monk seals. That does not change through the year, so go when the weather is best: August to September.
- When is the diving season in Kauai / Niihau?
- The diving season in Kauai / Niihau runs August to September.
- Is the diving in Kauai / Niihau good for beginners?
- It is better with some experience. It suits Advanced Open Water divers or equivalent, so newer divers should ask the local operator which sites fit their level.
- How warm is the water in Kauai / Niihau?
- Between 25 and 28 °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 Kauai / Niihau?
- A 5 mm full suit covers the coldest water of the year. In the warmest months a skin or 3 mm shorty is enough.
- What is the visibility like in Kauai / Niihau?
- Roughly 20 to 35 m depending on the month. That is estimated from satellite chlorophyll-a rather than measured in the water.
- What will I see diving Kauai / Niihau?
- The most consistently recorded species are Humpback whale (near-guaranteed), Spinner dolphin (near-guaranteed) and Green turtle (near-guaranteed), from 8,419 records within 60 km.
- Does Kauai / Niihau get tropical storms?
- Yes. Over 30 years of records a storm passed within 250 km in Jul, Oct, most often in July at 1 of 30 years.
- Is there current in Kauai / Niihau?
- 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 Kauai / Niihau?
- The site is closed Oct–Apr. September–May are the weakest months for conditions.
- How do you dive Kauai / Niihau?
- Mostly from day boats. Trips run through the season, Aug–Sep.