"We can get you to many places where you can have an Angkorian temple to yourself."- Andy Booth
Similar to Cambodia, Laos basically has two seasons; the dry season which runs from October through May and the wet season from May/June through September. Within the dry season you have the cooler months of December through February and then the temperatures steadily climb from March through May.
The early part of the rainy season also tends to be warmer, and rain showers are generally short and occur in the afternoon. Later in the rainy season the rain tends to be more frequent and showers can be longer and heavier. In northern Laos, rainfall is generally less heavy and it is more likely to rain at night or in the morning.
Across Laos, throughout much of the rainy season, expect temperatures of 29°C (84F) in the lowlands and 23°C (73F) in the valleys.