Updated Sun 06:35 (Pacific/Honolulu)
USA · Forecast updated Sep 27, 2026, 06:35 UTC
In the historical baseline for Big Island, typical monthly averages range from about 25.2°C (77.4°F) in February to 27.4°C (81.3°F) in September.
Northern Hemisphere. Summer is generally June–August; winter is December–February.
Average of 4 snorkeling spots around Big Island (Anaehoomalu Bay, Kahaluu Beach Park, Kealakekua Bay, Two Step Honaunau), from hourly observations for 2023–2025. The island pin is inland, so this uses the beaches. This is not this site's forecast archive.
| Month | Typical range | Average |
|---|---|---|
| January | 25.2–25.8°C | 25.5°C / 77.9°F |
| February | 25.1–25.4°C | 25.2°C / 77.4°F |
| March | 24.9–25.8°C | 25.3°C / 77.5°F |
| April | 25.0–26.2°C | 25.6°C / 78.1°F |
| May | 25.8–26.5°C | 26.2°C / 79.2°F |
| June | 26.4–26.9°C | 26.6°C / 79.9°F |
| July | 26.7–27.1°C | 26.9°C / 80.4°F |
| August | 27.0–27.4°C | 27.2°C / 81.0°F |
| September | 27.1–27.6°C | 27.4°C / 81.3°F |
| October | 27.1–27.4°C | 27.2°C / 81.0°F |
| November | 26.5–27.1°C | 26.8°C / 80.2°F |
| December | 25.9–26.4°C | 26.2°C / 79.2°F |
Source: Open-Meteo Marine API, MeteoFrance sea-surface temperature dataset. Equal-weight mean of those spots' coastal baselines. Each month is the mean of yearly monthly means; the range is the lowest and highest yearly monthly mean across those spots. 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 Big Island is 25.5°C (77.9°F), with yearly monthly means from 25.2–25.8°C.
Typical February water temperature near Big Island is 25.2°C (77.4°F), with yearly monthly means from 25.1–25.4°C.
Typical March water temperature near Big Island is 25.3°C (77.5°F), with yearly monthly means from 24.9–25.8°C.
Typical April water temperature near Big Island is 25.6°C (78.1°F), with yearly monthly means from 25.0–26.2°C.
Typical May water temperature near Big Island is 26.2°C (79.2°F), with yearly monthly means from 25.8–26.5°C.
Typical June water temperature near Big Island is 26.6°C (79.9°F), with yearly monthly means from 26.4–26.9°C.
Typical July water temperature near Big Island is 26.9°C (80.4°F), with yearly monthly means from 26.7–27.1°C.
Typical August water temperature near Big Island is 27.2°C (81.0°F), with yearly monthly means from 27.0–27.4°C.
Typical September water temperature near Big Island is 27.4°C (81.3°F), with yearly monthly means from 27.1–27.6°C.
Typical October water temperature near Big Island is 27.2°C (81.0°F), with yearly monthly means from 27.1–27.4°C.
Typical November water temperature near Big Island is 26.8°C (80.2°F), with yearly monthly means from 26.5–27.1°C.
Typical December water temperature near Big Island is 26.2°C (79.2°F), with yearly monthly means from 25.9–26.4°C.
Big Island snorkel report hub for Kona reefs, protected bays and lava-rock entries.
The water is typically warmest in September, at around 27.4°C (81.3°F) in the 2023–2025 historical baseline.
The water is typically coldest in February, at around 25.2°C (77.4°F) in the same historical baseline.
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