The climate varies with terrain, from tropical along the coast to semiarid and hot in the north. Exceedingly hot and humid, the coastal belt includes some of the wettest places on earth. For example, Debundscha, at the base of Mt. Cameroon, has an average annual rainfall of 405 inches (10,287 mm).
At 475,440 km2 (183,570 sq mi), Cameroon is the world's 54th largest country. It is slightly larger than the nation of Sweden and state of California. It is comparable in size to Papua New Guinea. Cameroon's landmass is 472,710 km2 (182,510 sq mi), with 2,730 km2 (1,050 sq mi) of water.
According to the 2010 revison of the World Population Prospects the total population was 19 599 000 in 2010, compared to only 4 466 000 in 1950. The proportion of children below the age of 15 in 2010 was 40.6%, 55.9% was between 15 and 65 years of age, while 3.5% was 65 years or older.