Samoa lies just west of the International Date Line and south of the equator. This location results in a tropical climate heavily influenced by the surrounding ocean. This environment creates year-round warmth, high humidity, and abundant rainfall, setting the stage for distinct seasonal patterns and the potential for severe weather events.
Defining the Tropical Marine Climate
Samoa’s climate is classified as tropical marine, characterized by minimal temperature fluctuation throughout the year. The Pacific Ocean acts as a thermal regulator, preventing extreme heat or cold. Daytime temperatures consistently range between 24°C and 30°C (75°F to 86°F), while nighttime temperatures rarely drop below 22°C (72°F).
This oceanic setting ensures the air is saturated with moisture, resulting in high relative humidity levels, often 80% or above. Water temperatures remain pleasant all year, averaging in the low 20s Celsius (low 70s Fahrenheit).
Seasonal Variation and Rainfall Patterns
The Samoan climate is marked by two distinct seasons defined by precipitation rather than temperature shifts. The wet season runs from November through April. During this time, the islands receive the majority of their annual precipitation, totaling between 270 and 419 millimeters (10.6 to 16.5 inches) per month. Rainfall often occurs in short, intense downpours that can cause localized flooding.
The dry season extends from May to October. Although named the dry season, precipitation still occurs, averaging between 133 to 257 millimeters (5.2 to 10.1 inches) monthly. Reduced rainfall and slightly lower humidity during this period make conditions more comfortable. Topography also influences precipitation, with windward sides receiving significantly more rainfall than leeward areas.
Tropical Storms and Cyclone Risks
Samoa is situated within the South Pacific cyclone belt, making tropical storms a meteorological hazard. The official cyclone season spans from November to April, aligning with the wet season. The highest risk for a named tropical cyclone typically occurs during the peak months of December, January, and February.
These systems bring destructive winds, intense rainfall, and storm surges. While the islands are not hit every year, there is a risk of one or fewer named tropical cyclones passing within a 400-kilometer radius during any season. The severity of the season is influenced by weather patterns like the El Niño Southern Oscillation (ENSO). For instance, a La Niña phase often brings above-average rainfall and an increased risk of severe events. Meteorological services monitor developing tropical depressions to provide warnings.