Thank you to Accuweather for its local free weather service information center; so we can so propose a 5 days projection of the weather in Luang Prabang. Many options available directly on the Accuweather website, do not hesitate to click on the link below: more information available there. Here also the average parameters of the weather in Luang Prabang (Thank you to NASA).
During the rainy season
Please notice that Luang Prabang has a microclimate, probably due to the general situation of the city (surrounded by mountains) and an exceptional local circumstances (the city has grown around the Phousi mountain).
So while the entire Southeast Asian region is regularly subject to torrential rains (sometimes causing flooding somewhat crippling for travelers), Luang Prabang has a very mild weather even during the monsoon. Most often the days are radiant, when nights are rainy and refreshing.