Nam Et-Phou Louey NPA generally has a high upland climate with two seasons: dry and rainy. The rainy season runs between April and September and the dry season between October and March. The average annual rainfall in Nam Et-Phou Louey is 1350 mm. In general rainfall is unevenly distributed throughout the year with peak rainfall occurring between June and August, and July having the highest number of rainy days with 21. The annual open pan evaporation is 900 mm, effectively limiting cultivation to the rainy season.
Forest & Flora
Based on satellite image interpretation in 1997 only 0.1% of the NPA is undisturbed primary forest and 23.2% is partially disturbed/open forest, indicating long-standing encroachment. The main part of the NPA is covered by shrub land (63.9%), comprising bushes mixed with tall grasses. This vegetation type has resulted from repeated use by shifting cultivators and is difficult to rehabilitate to forest.
There have been no detailed botanical surveys in the NPA excepting the Phou Louey Noy area, which indicated the presence of 314 plant species, 243 genera and 106 families. There are many plant species with known economic value: 18 are of use in construction, 26 for medicinal purposes, 39 as fuelwood, 46 for house decoration, 92 for consumption and 5 as poison. The uses, if any of the remaining 88 species are unknown.