As with all of mainland Southeast Asia, Laos experiences a tropical climate featuring wet and dry seasons. The wet monsoonal season starts as early as May and lasts until October. Although it can be cooler and the paddy fields take on a vibrant green, the rainy season is not the most popular time to visit Laos. This is not to say it is a poor time to visit just because rain lasts for hours rather than days, but the roads in the north can become impassable, trekking can be muddy and sodden and the humidity is inescapable.

November gives way to the cool, dry season, which runs through to April and is the high season in Laos. The skies take on a bright blue hue after the rains have totally dissipated and nights are generally wonderfully cool in hilly areas. December and January are the peak season, when hotels and tours must be booked in advance. Luang Prabang gets particularly busy during this time, especially around New Year.

It is wise to pack some cold weather clothing if you intend visiting northern areas during the peak season. The country stretches for several hundred miles north to south making it much warmer in the south during this time. The worst time to be in Laos is from March to May when it can become unbearably hot and humid, particularly in the north. It can also get very hazy due to slash and burn farming techniques. The water-throwing festival during Laos New Year in April brings a slight relief.