Samoa - Climate

Introduction

Western Samoa's climate is tropical. Although it is in the southern hemisphere, because of it's proximity to the equator there is no major seasonal difference such as the summer and winter that occurs in more temperate regions. There is however a rainy and a dry season and a slight difference in temperature associated with these. Another effect of being in the tropics is that the days and nights are of almost equal length, so if you want to get the most out the day you should really be an early riser.

Occaisonally Samoa is affected by a cyclone, most recently in 1993 the damage from that cyclone still being visible in some of the more remote areas such as Falealupo on Savai'i.

The islands are volcanic and there is an active volcano on Savai'i. The region does have occasional small tremors.

Current Weather in Apia

Rainfall.¹

Average monthly rainfall The rainy season in Samoa is centered around January and the dry season around July and August. Because the interior of the island is mountainous there is also a considerable difference between the rainfall on the coast and that in the jungle further inland. Northern and western shores receive about 100 inches (2.5 meters) and inland areas about 300 inches (7.5 meters) a year. If you are in Samoa during the rainy season you can expect to get wet on two out of three days.

Modified: 23rd November 1997

Temperature.²

There is very little seasonal difference in the temperature as, some shown by the graph below. During the period May - November the weather is slightly cooler because of the presence of the South East Trade Winds. Average Monthly Temperature, Apia

Modified: 23rd November 1997

Humidity.

I have been unable to locate a series of humidity data, but needless to say it is generally humid in Samoa with the humidity being at it's greatest in the rainy season, about 79%, and at about 73% in the dry season. It is not uncommon to change your clothes several times a day.

Cyclones.

Each year from 1989 to 1993 Samoa was hit by severe cyclones. The worst being Cyclone Val in 1992 which defoliated 90% of the island and destroyed about half of the islands coconut rees, which ultimately had a detrimental effect on the country's economy. Cyclones of this severity are, fortunately, unusual. The cyclone season is usually between January and March. There is currently some debate about whether this is likely to change because of a perceived permanency to the Southern Oscilation of the El Nino effect.

Modified: 23rd November 1997

Current Tropical Storm Tracks

Computer Generated Graphic from University of Hawaii (loaded into new browser window)

Current Satellite Images of South Pacific

CURRENTLY NOT AVAILABLE ftp://explorer.arc.nasa.gov/pub/Weather/GMS-5/gif/mapped/vis/globe/0latest.gif
Visible Spectrum (4 minutes download - loaded into new browser window)

IR Spectrum (4 minutes download - loaded into new browser window)

False colour satellite images of Samoa

Earthquakes.³

The Pacific is one of the most tectonically active areas of the world, being surrounded by the Ring of Fire and having numerous volcanic islands scattered across it. Compared to most areas in the Pacific, Samoa is relatively quiet. Below is a table of earthquakes from 1990 and a map showing their distribution relative to Samoa.

Date         Time         Lat      Lon    Depth  Mag          Location

1990/01/10 07:41:08.1  13.139S  172.612W  33.0 4.8Mb   MHDF SAMOA ISLANDS
1990/08/03 08:36:30.5  14.671S  173.388W  37.0 5.1Mb   MHDF SAMOA ISLANDS REGION
1990/09/26 20:10:41.9  14.736S  173.372W  33.0 5.0Mb   MHDF SAMOA ISLANDS REGION
1990/11/04 06:55:59.8  13.117S  173.466W  33.0 4.7Mb   MHDF SAMOA ISLANDS REGION
1990/12/11 18:55:35.4  14.885S  172.802W  33.0 4.6Mb   MHDF SAMOA ISLANDS
1991/02/22 20:14:28.3  14.750S  173.044W  33.0 4.1Mb   MHDF SAMOA ISLANDS REGION
1992/01/31 04:02:00.2  14.988S  173.048W  33.0 4.2Mb   MHDF SAMOA ISLANDS REGION
1993/05/03 23:15:06.6  14.404S  173.021W  23.0 5.1Mb   MHDF SAMOA ISLANDS REGION
1994/09/02 11:59:41.7  14.909S  172.122W  35.0 4.2Mb   MHDF SAMOA ISLANDS
1995/10/03 01:00:20.7  13.865S  171.299W  38.0 4.9Mb   MHDF SAMOA ISLANDS
1995/10/06 22:35:05.0  14.917S  173.472W  33.0 4.5Mb   MHDF SAMOA ISLANDS REGION
1996/05/10 22:05:57.7  14.871S  173.420W  33.0 4.2Mb   WHDF SAMOA ISLANDS REGION
1996/05/26 03:17:02.2  14.973S  173.314W  33.0 3.9Mb   WHDF SAMOA ISLANDS REGION
1996/06/15 02:43:25.6  14.941S  173.145W  33.0 4.6Mb   WHDF SAMOA ISLANDS REGION
1996/06/30 22:04:49.5  14.968S  172.756W  33.0 4.8Mb   WHDF SAMOA ISLANDS
1996/07/24 11:34:18.3  14.658S  172.950W  33.0 4.7Mb   WHDF SAMOA ISLANDS
1996/09/24 23:19:05.1  14.999S  173.041W  33.0 0.0     WHDF SAMOA ISLANDS REGION

Modified: July 23rd 1998

Tsunami.

Another consequence of being located in the Pacific and being surrounded by the Ring of Fire, is the occurence of tsunami, also erroneously called tidal waves. These arise when an underwater earthquake causes an upwards or downwards movement in land or an underwater landside. This can lead to a large movement of water which is undetectable in the open ocean, but rises to form a massive wave when it encounters shallower coastal waters.

Fortunately these are rather rare and Samoa is part of a Pacific wide monitoring and alert system, so any events that are likely to lead to a tsunami are quickly relayed to the radio and television stations.

In the event of a confirmed tsunami you should head for high ground or get as far away from the coast as you can. This is not difficult to do in Samoa since there is only a narrow coastal strip around most of the islands and then it rises to inland mountains.
Sometimes a tsunami is preceeded by an emptying of the lagoon as the water rushes out. DO NOT STOP TO WATCH OR EXPLORE THE LAGOON. Tsunami travel at several hundred miles an hour and before you know it you could be caught by the wave.
Once the wave has struck, do not assume that you can go back to the shore. Quite often there can be a series of waves seperated by 20 minutes to half an hour. Only go back when the emergency services say it is safe.

Added: 25th October 1998

Volcanoes.
The have been three volcanic eruptions on Savai'i in recent times. Mount Matavanu was last active between 1905 and 1910. Mount Mu erupted in 1902. Mount Afi erupted last some time around 1690.

Added: 24th November 1997

¹ Source: The Global Historical Climatology Network -GHCN version 1
² Source: Pacific Daily Rainfall Data
³ Source: The IRIS Earthquake Database Search Engine

There is an observatory on the outskirts of Apia gathering seismic, oceanographic, meteorological and hydrographic data. If anyone knows if this data is available on the internet could you please let me know.

Reformatted: 4th May 2004