Except for the narrow piedmont coastal plains, the terrain is dominated by hills and the Annamite Mountains. The highlands, characterized by steep slopes, sharp crests, and narrow valleys, are covered mainly by a dense broadleaf evergreen forest. Most of the peaks are from 4,000 feet (1,200 m) to 7,000 feet (2,100 m) feet high, but some rise above 8,000 feet (2,400 m). The narrow coastal plains flanking the highlands on the east have rocky headlands and consist of belts of sand dunes and, in areas where the soil is suitable, rice fields. From the crests that mark the drainage divide in the highlands, streams flow either east towards the South China Sea or west into Laos or Cambodia. Those flowing eastward follow short courses through deep narrow valleys over rocky bottoms until they reach the coastal plains, where they slow down and disperse. The westward flowing streams follow longer traces, sometimes through deep canyons which are subject to seasonal flooding.
The weather features a wide range of temperatures and rainfall, with hot and dry south-west winds during the Southwest Monsoon (May through September), and much cooler wet weather during the rainy season (November to mid-March). Annual average temperature is 24 °C (75°F), but temperatures can drop as low as 7°C (45°F) during the rainy season.