Most of the year is hot and humid. Laos enjoys a tropical climate with two distinct seasons. The rainy season is from the beginning of May to the end of September, and the dry season is from October through April. The yearly average temperature is about 28 degrees Celsius, rising to a maximum of 38 degrees Celsius during April and May.
In Vientiane a minimum temperature of 19 degrees Celsius is to be expected during January. In mountainous areas, however, temperature drops to as low as 14-15 degrees Celsius during the winter months, and during cold nights, can easily reach the freezing point. The average precipitation is highest in Southern Laos, where the Annamite Mountains receive over 3,000 mm. annually. In Vientiane rainfall is about 1,500-2,000 mm., and in the Northern provinces only 1,000-1,500 mm.