Thanks to the North Pacific current that flows from the western coast of North America towards the Hawaiian Islands, water temperatures near the shores remain pleasant year-round, with average temperatures ranging from 24°C to 27°C (76-81°F). Still, water temperatures in Hawaii differ by a few degrees throughout the archipelago. For example, in Kauai, the northernmost of the main islands, water temperatures range from 25°C to 28°C (77-83°F), whereas on the beach resort side of the Big Island, they range from 25°C to 27°C (77-81°F).
The coldest months are January through April, and the warmest are September and October. Knowing the water temperature at the time of your trip will help you determine whether 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 affects underwater visibility, must be taken into account. In this case, it is better to check the Hawaii climate information.