Thanks to the North Pacific current that flows from the western coast of North America towards the Hawaiian islands, the Pacific Ocean water temperatures near the shores remain pleasant year-round, with average temperatures going from 24°C (76°F) to 27°C (81°F). Still, Hawaii water temperatures differ by a few degrees throughout the archipelago.
For example, in Kauai, which is the northernmost of the main islands, water temperatures range from 25°C (77°F) to 28°C (83°F), but on the beach resort side of Big Island, water temperatures range between 25°C (77°F) and 27°C (81°F).
The coldest months are from January to April, and the warmest months are September and October. Knowing what the water temperature will be at the time of your trip will help you determine if this is the best time to dive in Hawaii. Note that humpback whales visit the Hawaiian archipelago from November to April, with a peak season in February and March.
Hawaii average temperature table
You will find below, month by month, the average water temperature in Hawaii:
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sept | Oct | Nov | Dec |
| 24°C 76°F | 24°C 75°F | 24°C 75°F | 25°C 76°F | 25°C 77°F | 26°C 78°F | 26°C 78°F | 26°C 79°F | 27°C 80°F | 26°C 79°F | 26°C 78°F | 24°C 76°F |
Hawaii weather data source: seatemperature.org
Oahu water temperature
You will find below, month by month, the average water temperature in Oahu:
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sept | Oct | Nov | Dec |
| 24°C 76°F | 24°C 76°F | 24°C 76°F | 25°C 77°F | 25°C 77°F | 26°C 78°F | 26°C 78°F | 26°C 78°F | 27°C 81°F | 26°C 78°F | 26°C 78°F | 25°C 77°F |
Oahu weather data source: seatemperature.org
Maui water temperature
You will find below, month by month, the average water temperature in Maui:
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sept | Oct | Nov | Dec |
| 25°C 77°F | 25°C 77°F | 25°C 77°F | 25°C 77°F | 25°C 77°F | 26°C 78°F | 26°C 78°F | 26°C 78°F | 27°C 81°F | 27°C 81°F | 26°C 78°F | 25°C 77°F |
Maui weather data source: seatemperature.org
Big Island water temperature
You will find below, month by month, the average water temperature in Big Island:
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sept | Oct | Nov | Dec |
| 25°C 77°F | 25°C 77°F | 25°C 77°F | 25°C 77°F | 25°C 77°F | 26°C 78°F | 26°C 78°F | 27°C 81°F | 27°C 81°F | 26°C 78°F | 26°C 78°F | 25°C 77°F |
Big Island weather data source: seatemperature.org
Other factors, of course, such as rainfall, which impacts the level of visibility underwater, must be taken into account. In this case, it is better to check Hawaii climate information.