Vang Vieng in July

November through April delivers perfect weather - sunny days around 28°C and cool evenings. This is peak season, so book accommodation ahead and expect higher prices. December and January see the most crowds but also the clearest skies for mountain views. May through October brings the rainy season. Afternoon downpours turn dirt roads into mud pits and some caves close due to flooding. But you'll have the place mostly to yourself and room rates drop 40%. The landscape turns incredibly green and waterfalls run full. Avoid Chinese New Year (late January/early February) when domestic tourists flood in. Hotel prices triple and the tubing operators get overwhelmed. Similarly, skip Lao New Year in April unless you enjoy water fights and inflated prices.