Cambodia’s climate is governed by the monsoon winds, which define two major seasons. From mid-May to early October, the strong prevailing winds of the southwest monsoon bring heavy rains and high humidity. From early November to mid-March, the lighter and drier winds of the northeast monsoon bring variable cloudiness, infrequent precipitation, and lower humidity. The weather between these seasons is transitional. Maximum temperatures are high throughout the year, ranging from about 82 to 83 °F (28 °C) in January, the coolest month, to about 95 °F (35 °C) in April. Annual precipitation varies considerably throughout the country, from more than 200 inches (5,000 mm) on the seaward slopes of the southwestern highlands to about 50–55 inches (1,270–1,400 mm) in the central lowland region. Three-fourths of the annual rainfall occurs during the months of the southwest monsoon.

Plant and animal life

Although much of Cambodia is heavily forested, the central lowland region is covered with rice paddies, fields of dry crops such as corn (maize) and tobacco, tracts of tall grass and reeds, and thinly wooded areas. Savanna grassland predominates in the transitional plains, with the grasses reaching a height of 5 feet (1.5 meters). In the eastern highlands the high plateaus are covered with grasses and deciduous forests. Broad-leaved evergreen forests grow in the mountainous areas to the north, with trees 100 feet (30 meters) high emerging from thick undergrowths of vines, rattans, palms, bamboos, and assorted woody and herbaceous ground plants. In the southwestern highlands, open forests of pines are found at the higher elevations, while the rain-drenched seaward slopes are blanketed with virgin rainforests growing to heights of 150 feet (45 meters) or more. Vegetation along the coastal strip ranges from evergreen forests to nearly impenetrable mangroves.

The northeastern forests of Cambodia—like the neighboring areas of Laos and Vietnam—once sheltered large populations of wild animals such as elephants, wild oxen, rhinoceroses, and several species of deer, but the loss of forest cover, combined with warfare and unregulated hunting in the region, sharply reduced those numbers. Small populations of most of these species may still be found, along with some tigers, leopards, bears, and many small mammals. Among the more common birds are herons, cranes, grouse, pheasant, peafowl, pelicans, cormorants, egrets, and wild ducks. Four varieties of snakes are especially dangerous: the Indian cobra, the king cobra, the banded krait, and Russell’s viper.

Ethnic groups

The Khmer (Cambodians) account for the vast majority of the population, producing a homogeneity unique in Southeast Asia that has encouraged a strong sense of national identity. Ethnic minorities include Chinese, Vietnamese, Muslim Cham-Malays, Laotians, and various indigenous peoples of the rural highlands.

The Khmer, who belong to the Mon-Khmer ethnolinguistic group, are concentrated in the lowland regions surrounding the Mekong River and the Tonle Sap, on the transitional plain, and along the coast. The product of centuries of intricate cultural and ethnic blending, the Khmer moved southward before 200 bce into the fertile Mekong delta from the Khorat Plateau of what is now Thailand. They were exposed to successive waves of Indian influence and, in the 8th century ce, to Indo-Malayan influence, perhaps including immigration from Java. Immigrations of Tai peoples occurred from the 10th to the 15th century, of Vietnamese beginning in the 17th century, and of Chinese in the 18th and 19th centuries.

Among the ethnic minorities in Cambodia before 1975, the Chinese were the most important, for they controlled the country’s economic life. They were shunted aside in the communist-led revolution of the 1970s and made to become ordinary peasants. Those who did not seek refuge abroad after 1975 and others who subsequently returned regained some of their former influence as urban centers were revived.

The Vietnamese minority occupied a somewhat lower status than the Chinese, and most of them fled or were repatriated to Vietnam after 1970. In the 1980s, however, a large number of Vietnamese migrants, many of them former residents of Cambodia, settled in the country. Centuries of mutual dislike and distrust have clouded Vietnamese-Khmer relations, and intermarriage has been infrequent.

The most important minority in the early 21st century was the Cham-Malay group. Known in Cambodia as Khmer Islam or Western Cham, the Cham-Malay group also maintained a high degree of ethnic homogeneity and was discriminated against under the regime of Democratic Kampuchea. Receiving only slightly better treatment than the Khmer Islam during that period were the smaller communities of indigenous peoples. These communities, known collectively as Khmer Loeu (“Upland Khmer”), include the Katu, Mnong, Stieng, Jarai, and Rhadé, among others, and inhabit the sparsely populated northeastern provinces bordering Vietnam and Laos.

Languages

The Khmer language is one of the major tongues of the Mon-Khmer subfamily of the Austroasiatic language family and is spoken by nearly all people in Cambodia, including the Cham-Malay. Historically, a small number of people in Cambodia spoke Vietnamese and Chinese. The Katu, Mnong, and Stieng speak Mon-Khmer languages, while the Jarai and Rhadé speak languages of the Austronesian language family.