Guam Geography and Climate

By | August 8, 2021

Guam geography

Guam is the southernmost island of Micronesia and belongs to the territory of the United States. The largest island in the Mariana Archipelago with 544 square kilometers is located in the western Pacific Ocean and is inhabited by almost 180,000 people. Guam, which belongs to the outskirts of the USA, is geographically assigned to the island region of Micronesia. The island is located about 2,500 kilometers south of Japan, 2,400 kilometers east of the Philippines and about 5,300 kilometers west of Hawaii.

The island is only 48 kilometers long and 15 kilometers wide and is of volcanic origin. Guam consists of an flaugh limestone plateau, which slopes in the north of the island in rugged cliffs to the sea and has only a narrow coastal plain. The inland is predominantly dominated by gently rolling hills, while the south of Guam consists of a mixture of high volcanic mountains and deeply carved valleys, which are cut by numerous rivers and waterfalls. The island is almost completely enclosed by reefs. The beaches on the west coast of Guam are quieter, while those on the east coast are lapped by strong waves. Only the southernmost tip of the island has somesheltered bays.

According to, Guam is in a zone where earthquakes are rare but not unknown. On August 8, 1993, the island was shaken by the most violent earthquake that struck Micronesia in this century. The quake reached a magnitude of 8.2 on the Richter scale and had its origin in the depths of the Mariana Trench, where volcanic activity is the order of the day, but is mostly “buffered” by the depth and breadth of the world’s largest ocean.
The total coastline of Guam extends to 125.5 kilometers. At 406 meters, Mount Lamlam is the highest point on Guam.

Guam climate

Due to its proximity to the equator, the island of Guam has a tropical, warm and always humid climate all year round, which also has a high level of humidity. The average temperatures are around 27 ° C. The thermometer rarely rises above 30 ° C during the day. At night, however, the temperature hardly falls below 21 ° C. Guam is one of the wettest areas on earth. “Only” 4,000 mm fall annually on the coast and in the central part. In the higher elevations in the south of the island, up to 5,500 mm of precipitation is measured each year.

The climate of Guam is characterized by two seasons.

The drier season runs from January to June. The high humidity also decreases in the first half of the year. But rains are completely normal during this period as well. But after the usually short showers, the sun quickly shines again.

It looks completely different in the humid half of the year between July and December. Then the trade winds from the northeast blow humid air masses over the island. It is often cloudy and there are violent tropical thunderstorms and showers in the late afternoon and early evening almost every day. In the wet season it is possible that typhoons also haunt Guam. In relation to other countries in this part of the world, the island is only hit by a tropical cyclone every eighth year on average.

Best travel time for Guam

Experts consider January to June to be the ideal time to visit Guam. The weather is then drier and cooler in the first few months, but still warm. The sun often shines from a blue sky all day long, so there are optimal conditions for swimming, diving and sailing.

The rare typhoons then also disappeared. These can occur in the second half of the year. In addition, tropical showers and thunderstorms often fall, it gets hot and humid. It is therefore not advisable to travel during these months.

Guam – key data

Area: 544 km²

183,286 residents (July 2011 estimate, CIA). Chamorro 37.1%, Filipino 26.3%, other Pacific islanders 11.3%, whites 6.9%, other Asians 6.3%, other ethnic groups 2.3%, mixed roots 9.8% (2000 census )

Population density: 337 residents per km²

Population growth:
1.314% per year (2011, cIA)

Capital: Hagatna (1,100 residents, 2000)

Largest city: Dededo (42,980 residents, 2000)

Highest point:
Mount Lamlam, 406 m

Lowest point: Pacific Ocean, 0 m

Form of government: Guam is a non-incorporated territory of the USA and is administered by the US Department of the Interior. Internal affairs have been self-determined since 1950.

The Guam Parliament consists of a chamber with 15 members (senators) who are elected for two years. The island sends a (non-voting) MP to the US House of Representatives. The residents of Guam have the status of US citizens.

Administrative division: 19 municipalities: Agana Heights, Agat, Asan-Maina, Barrigada, Chalan Pago-Ordot, Dededo, Hagåtña, Inarajan, Mangilao, Merizo, Mongmong-Toto-Maite, Piti, Santa Rita, Sinajana, Talofofo, Tamuning (with Tumon ), Umatac, Yigo, Yona

Head of State: US President Barack Obama, since January 20, 2009

Head of Government: Governor Felix Perez Camacho, since January 6, 2003

Language: The official languages ​​in Guam are English (38.3%) and Chamorro (22.2%). Other languages: Filipino languages ​​(22.2%), languages ​​of other Pacific islands (6.8%), other Asian languages ​​(7%), other languages ​​(3.5%). (2000 census)

Religion: Roman Catholic (85%), Other (15%). (1999 estimate)

Local time: CET + 9 h.
There is no changeover between summer and winter time on Guam.
The time difference to Central Europe is + 9 h in winter and + 8 h in summer.

International phone code: +1 (671)

Internet code Mains

Voltage: 120 V, 60 Hz

Guam Geography and Climate