Laos generally enjoys a mild tropical climate, but it can get quite chilly in the cool season. Temperatures range from 10 – 40 degrees Celsius in the Mekong Valley, and may dip below zero in the mountains and on the Xieng Khouang and Bolaven Plateaus. There are two distinct seasons – dry season from October - April, including cool from November - February and the rainy season which lasts from May - September.