Tonga

Best Time to Dive in Tonga

18.66°S 173.97°W

Go August to September. Conditions are at their best and the humpback whale season is on.

Best time
Aug–Sep
Water
26–29 °C
Visibility
0–25 m
Season runs
Mar–Nov
Dived from
day boat
Tidal range
0.7–1.1 m
Species logged
2

Worth knowing: 59% of days see seas over 1.5 m.

Where it is

Tonga
25 kmN

111 km across · coastline from Natural Earth 10m

Diving in Tonga — monthly breakdown

Best months at this destination

A year of scuba diving conditions at a glance. Hover a month to isolate it.

Month by month conditions, water temperature, visibility and marine life
JanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecember
ConditionsPoorPoorPoorPoorPoorPoorPoorExcellentExcellentPoorPoorPoor
Water temp (°C)282929282827262626272728
Visibility (m)0–10—5–155–150–1015–255–155–155–15—0–105–15
Marine lifeQuietQuietQuietQuietQuietQuietQuietPeakPeakQuietQuietQuiet
Best timePeakPeak
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 Tonga diving season

2 seasons

August to September · Peak season

2 months
Water temperature
26–26 °C
Rain
10 days a month

Diving conditionsIt rains less. The wind is up.

October to July · Off season

10 months
Water temperature
26–29 °C
Rain
16 days a month

Diving conditionsIt rains more.

  • Water temperature is satellite sea-surface temperature, so expect it cooler below the thermocline.
  • Visibility is estimated from satellite chlorophyll-a.

Tonga water temperature and weather

1,371 underwater observation records · 30 surveyed years of ocean data · 10 years of sea temperature

Water & weather

Tonga water temperature by month

The dashed line is the monthly average. Eight days in ten fall inside the band.

252627282930JanFebMarAprMayJunJulAugSepOctNovDecSea temperature (°C)

10th to 90th percentile rangemonthly mean

13
rough days a month

Seas top 1.5 m on 43% of days. Enough to cancel a day boat

4
blowy days a month

Gusts over 40 km/h, about where a day boat stays in port

15
wet days a month

4 of them bring heavy rain

Monthly sea state, wind, rain, air temperature and daylight
MonthSwellGusts over 40 km/hWet daysHeavy rainAirDaylight
January1.8 m9%19728 °C13.0 h
February2.0 m17%191028 °C12.6 h
March1.7 m3%20728 °C12.1 h
April1.9 m14%16527 °C11.6 h
May2.3 m21%15327 °C11.1 h
June2.0 m18%11326 °C10.9 h
July2.2 m22%10225 °C11.0 h
August2.1 m18%11225 °C11.4 h
September2.1 m15%9225 °C11.9 h
October2.0 m20%13326 °C12.4 h
November2.0 m11%14326 °C12.9 h
December1.9 m11%18627 °C13.1 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.

Conditions by week, four weeks per month
Week 1January week 1: PoorFebruary week 1: PoorMarch week 1: PoorApril week 1: ModerateMay week 1: PoorJune week 1: PoorJuly week 1: PoorAugust week 1: ExcellentSeptember week 1: GoodOctober week 1: PoorNovember week 1: PoorDecember week 1: Poor
Week 2January week 2: PoorFebruary week 2: PoorMarch week 2: ModerateApril week 2: PoorMay week 2: PoorJune week 2: PoorJuly week 2: PoorAugust week 2: GoodSeptember week 2: GoodOctober week 2: PoorNovember week 2: PoorDecember week 2: Poor
Week 3January week 3: PoorFebruary week 3: PoorMarch week 3: PoorApril week 3: PoorMay week 3: ModerateJune week 3: ModerateJuly week 3: ModerateAugust week 3: GoodSeptember week 3: ExcellentOctober week 3: PoorNovember week 3: PoorDecember week 3: Poor
Week 4January week 4: PoorFebruary week 4: PoorMarch week 4: PoorApril week 4: PoorMay week 4: PoorJune week 4: PoorJuly week 4: PoorAugust week 4: GoodSeptember week 4: GoodOctober week 4: PoorNovember week 4: PoorDecember week 4: Poor
Excellent Good Moderate PoorBest week to go: third of September

September, week by week

WeekConditionsWaterSwellWindRain chance
Week 1Good26 °C2.0 m33 km/h30%
Week 2Good26 °C2.0 m32 km/h35%
Week 3Excellent26 °C2.2 m33 km/h30%
Week 4Good26 °C2.3 m34 km/h27%

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.

Wetsuit thickness by month
JanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecember
SuitJanuary: skinFebruary: skinMarch: skinApril: skinMay: 3 mmJune: 3 mmJuly: 3 mmAugust: 3 mmSeptember: 3 mmOctober: 3 mmNovember: 3 mmDecember: skin
  • Dec–Aprskin or 3 mm shorty
  • May–Nov3 mm full suit

Swell through the year

The rough end of each month — nine days in ten come in under it.

JanJanuary: 1.8 metresFebFebruary: 2.0 metresMarMarch: 1.7 metresAprApril: 1.9 metresMayMay: 2.3 metresJunJune: 2.0 metresJulJuly: 2.2 metresAugAugust: 2.1 metresSepSeptember: 2.1 metresOctOctober: 2.0 metresNovNovember: 2.0 metresDecDecember: 1.9 metres

Amber is over 1.5 m.

Tides

springs 1.2 mneaps 0.7 mneapsone lunar month
Daily tidal range across one lunar month.

Tropical storms

7 of the last 30 Januarys saw a tropical storm pass within 250 km. Anything has been recorded Dec–Feb, Apr.

JanJanuary: 7 of 30 yearsFebFebruary: 6 of 30 yearsMarMarch: 0 of 30 yearsAprApril: 2 of 30 yearsMayMay: 0 of 30 yearsJunJune: 0 of 30 yearsJulJuly: 0 of 30 yearsAugAugust: 0 of 30 yearsSepSeptember: 0 of 30 yearsOctOctober: 0 of 30 yearsNovNovember: 0 of 30 yearsDecDecember: 5 of 30 years

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

Tonga marine life — what you'll see diving

1,371 records within 60 km
SpeciesWhenObserved windowReliabilityEvidenceRecords
Humpback whaleAug–SepNear-guaranteed
29/30
1324
Sperm whaleMar, AugHit-or-miss
3/30
18
Peak Present No survey data
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 Tonga — common questions

When is the best time to dive Tonga?
Go August to September. Conditions are at their best and the humpback whale season is on.
When is the diving season in Tonga?
The diving season in Tonga runs March to November, and it is at its best August to September.
Is the diving in Tonga good for beginners?
Yes. It is known as a snorkelling site as much as a dive site, so no experience is needed to get in the water.
How warm is the water in Tonga?
Between 26 and 29 °C at the surface across the year, coldest in August and warmest in February. It runs cooler below the thermocline.
What wetsuit do I need in Tonga?
A 3 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 Tonga?
Roughly 0 to 25 m depending on the month. That is estimated from satellite chlorophyll-a rather than measured in the water.
What will I see diving Tonga?
The most consistently recorded species are Humpback whale (near-guaranteed) and Sperm whale (hit-or-miss), from 1,371 records within 60 km.
Does Tonga get tropical storms?
Yes. Over 30 years of records a storm passed within 250 km in Dec–Feb, Apr, most often in January at 7 of 30 years.
Is there current in Tonga?
The tide rises and falls 1.1 m around the full and new moon, against 0.7 m in between. How much of that becomes current depends on the shape of the channel.
When should I avoid Tonga?
October–July are the weakest months for conditions.
How do you dive Tonga?
Mostly from day boats. Trips run through the season, Mar–Nov.