Updated Thu 11:21 (Australia/Brisbane)
Australia · Forecast updated Sep 17, 2026, 11:21 UTC
Current Sea Temperature
24.0°C
75.2°F
Mild water
Valid Sep 17, 2026, 11:21 (Australia/Brisbane). Source: stored Open-Meteo marine forecast. Temperature is not a safety rating or snorkel score.
Versus this month's average
0.8°C below
The typical September average is 24.8°C (76.6°F) from the historical baseline.
Recent trend
At least two weeks of records are needed before showing a reliable trend.
What to wear
Mild water
A rash guard is useful; cold-sensitive snorkelers may prefer a shorty wetsuit.
Cold tolerance varies. Wind, session length, sunshine, and exertion also affect comfort; temperature alone does not describe sea conditions or replace the snorkel forecast.
Cairns is a mainland gateway. Reef water a short boat ride east can differ from Trinity Inlet. Use the monthly profile as a regional guide, then check Green Island, Fitzroy Island or an outer-reef forecast for the water you will enter.
In the historical baseline for Cairns, typical monthly averages range from about 23.6°C (74.5°F) in August to 30.4°C (86.7°F) in January.
Over the past 30 days, the average sea temperature in Cairns has been 24.0°C.
Southern Hemisphere. Summer is generally December–February; winter is June–August.
Typical monthly sea-surface temperature near Cairns, calculated from hourly observations for 2023–2025. This is not this site's forecast archive.
| Month | Typical range | Average |
|---|---|---|
| January | 29.6–31.0°C | 30.4°C / 86.7°F |
| February | 29.4–30.7°C | 30.1°C / 86.2°F |
| March | 29.2–29.6°C | 29.4°C / 84.9°F |
| April | 28.0–29.2°C | 28.5°C / 83.3°F |
| May | 25.6–26.2°C | 25.8°C / 78.4°F |
| June | 24.1–24.5°C | 24.3°C / 75.7°F |
| July | 23.7–24.1°C | 23.9°C / 75.0°F |
| August | 23.1–24.1°C | 23.6°C / 74.5°F |
| September | 24.4–25.3°C | 24.8°C / 76.6°F |
| October | 26.0–27.4°C | 26.8°C / 80.2°F |
| November | 27.5–29.9°C | 28.6°C / 83.5°F |
| December | 28.7–30.2°C | 29.5°C / 85.1°F |
Source: Open-Meteo Marine API, MeteoFrance sea-surface temperature dataset. Nearest sea grid cell (-16.96, 145.96). Each month is the mean of yearly monthly means; the range is the lowest and highest of those yearly monthly means. Open-Meteo methodology.
Each month uses the 2023–2025 baseline. The range is the lowest and highest yearly monthly mean, not an hourly extreme.
Typical January water temperature near Cairns is 30.4°C (86.7°F), with yearly monthly means from 29.6–31.0°C.
Typical February water temperature near Cairns is 30.1°C (86.2°F), with yearly monthly means from 29.4–30.7°C.
Typical March water temperature near Cairns is 29.4°C (84.9°F), with yearly monthly means from 29.2–29.6°C.
Typical April water temperature near Cairns is 28.5°C (83.3°F), with yearly monthly means from 28.0–29.2°C.
Typical May water temperature near Cairns is 25.8°C (78.4°F), with yearly monthly means from 25.6–26.2°C.
Typical June water temperature near Cairns is 24.3°C (75.7°F), with yearly monthly means from 24.1–24.5°C.
Typical July water temperature near Cairns is 23.9°C (75.0°F), with yearly monthly means from 23.7–24.1°C.
Typical August water temperature near Cairns is 23.6°C (74.5°F), with yearly monthly means from 23.1–24.1°C.
Typical September water temperature near Cairns is 24.8°C (76.6°F), with yearly monthly means from 24.4–25.3°C.
Typical October water temperature near Cairns is 26.8°C (80.2°F), with yearly monthly means from 26.0–27.4°C.
Typical November water temperature near Cairns is 28.6°C (83.5°F), with yearly monthly means from 27.5–29.9°C.
Typical December water temperature near Cairns is 29.5°C (85.1°F), with yearly monthly means from 28.7–30.2°C.
These values come from hourly forecasts SnorkelForecast has stored. They cover only months with records and do not replace the historical baseline.
| Month | Min | Average | Max |
|---|---|---|---|
| September | 23.5°C / 74.3°F | 23.8°C / 74.8°F | 24.1°C / 75.4°F |
Partial coverage: 1 calendar months with records. Profile calculated from 74 hourly forecast records across 1 monthly periods. This is a growing archive, not a long-term climate normal.
Cairns is the main gateway for inner and outer Great Barrier Reef snorkel trips. Use the reef and island reports below for the day's wind, swell and water temperature, not this harbour forecast alone.
The current sea surface temperature near Cairns is 24.0°C (75.2°F). Over the last 30 days, the average has been 24.0°C.
The water is typically warmest in January, at around 30.4°C (86.7°F) in the 2023–2025 historical baseline.
The water is typically coldest in August, at around 23.6°C (74.5°F) in the same historical baseline.
At 24.0°C, the water is usually comfortable for swimming and snorkeling.
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See how today's sea temperature, wave height, wind, and tides combine into a detailed snorkeling score for Cairns.
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