Country

Samoa

Explore historical and projected climate data, climate data by sector, impacts, key vulnerabilities and what adaptation measures are being taken. Explore the overview for a general context of how climate change is affecting Samoa.

Current Climate Climatology

This page presents Samoa's climate context for the current climatology, 1991-2020, derived from observed, historical data. Information should be used to build a strong understanding of current climate conditions in order to appreciate future climate scenarios and projected change. You can visualize data for the current climatology through spatial variation, the seasonal cycle, or as a time series. Analysis is available for both annual and seasonal data. Data presentation defaults to national-scale aggregation, however sub-national data aggregations can be accessed by clicking within a country, on a sub-national unit.  Other historical climatologies can be selected from the Time Period dropdown list. Data for  specific coordinates can be downloaded for in the Data Download page.

Observed, historical data is produced by the Climatic Research Unit (CRU) of University of East Anglia. Data is presented at a 0.5º x 0.5º (50km x 50km) resolution.

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Climate Data Historical

Samoa’s climate is typical of that associated with small tropical islands, and is characterized by high rainfall and humidity, near-uniform temperatures throughout the year, winds dominated by the south-easterly trade winds (which are directly associated with the South Pacific Convergence Zone), and the occurrence of tropical cyclones during the southern-hemisphere summer. There are two seasons, marked by significant differences in rainfall: Samoa’s wet season lasts from November to April and its dry season starts in May and ends in October. The annual rainfall total is about 3,000 mm (varying from 2,500 mm in the northwest parts of the main islands to over 6,000 mm in the highlands of Savai’i), and about 75% of the precipitation occurs between November and February. Samoa’s topography has a significant effect on rainfall distribution – because of a predominant easterly wind, the mountain ranges determine the distribution of rainfall. Wet areas are generally those located in the southeast and the relatively drier areas are located in the northwest. Samoa is also vulnerable to anomalously long dry spells that coincide with the El Niño Southern Oscillation (ENSO). The temperature in Samoa is typically tropical (ranging from 24°C-32°C daily) and generally constant during the entire year with little seasonal variation due to Samoa’s near-equatorial location. Observations from the Meteorological Office at Mulinu’u have revealed that the highest mean temperature of 27.1°C occurs between December and March, while the lowest mean temperature of 26.0°C occurs between July and September.

Temperature

  • There has been increased inter-annual variability and significant upward trend in maximum temperatures over the last thirty years.
  • The mean annual temperature has increased by 0.59°C, with the minimum and maximum temperature increasing by 0.67°C and 0.18°C, respectively, and across the Pacific, the numbers of hot days and hot nights have increased significantly.
  • Mean air temperature trends show little change at Apia, the country’s capital, since 1957, the annual number of Cool Days has decreased significantly, and inter-annual variability is evident in maximum air temperatures for the city.
  • A significant increase in the rate of warming post-1980, suggesting that the over the subsequent 40 year period the climate in the vicinity of Samoa warmed by approximately 0.6°C.

Precipitation

  • There has been little change in extreme daily rainfall amounts since 1961 and November–April rainfall since 1890.
  • Maximum daily rainfall recorded in Apia over the last forty-eight years show a large range of inter-annual variability, which has become more pronounced in the last twenty years such that daily rainfall of at least 200 mm is more common.
  • Meteorological data of Samoa collected over 101 years indicate a decreasing trend in precipitation by 49.28 mm, annual and May–October rainfall has increased at Apia since 1890 (and is statistically significant at the 5% level). This is most likely due to a shift in the mean location of the South Pacific Convergence Zone (SPCZ) towards Samoa and/or there being a change in the intensity of rainfall associated with the SPCZ over the 122 year period.
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