The topography includes volcanic origin, surrounded by coral reefs with relatively flat coralline limestone plateau (source of most fresh water), with steep coastal cliffs and narrow coastal plains in north, low hills in center, mountains in south. The average density of population is approximately 307 per km². The notable climate conditions in Guam can be described as tropical marine with generally warm and humid, moderated by northeast trade winds, dry season (January to June), rainy season (July to December) and little seasonal temperature variation. Possible natural disasters include frequent squalls during rainy season or relatively rare but potentially destructive typhoons (June - December).

To reach someone in Guam dial +1-671 prior to a number. There are 65,500 installed telephones. And there are 98,000 registered mobile phones. The cellular networks commonly support frequencies of 1900 MHz. Websites registered in this country end with the top level domain ".gu". If you want to bring electric equipment on your trip (e.g. laptop power supply), note the local power outlet of 110V - 60Hz.