Rainfall averages 800 mm per year, falling mostly during the summer rainy season.

Characteristic trees of the lowlands, typically on limestone-derived soils, are Brosimum alicastrum, Sideroxylon persimile, Godmania aesculifolia, Manilkara zapota, Pterocarpus acapulcensis, Licania arborea, Tabebuia palmeri, Pseudobombax palmeri, Bombax ellipticum, and Plumeria rubra.

Foothill forests on soils derived from igneous rocks include Lysiloma divaricatum, Bursera excelsa, and Bursera fagaroides, with Ceiba aesculifolia, Comocladia macrophylla, and Trichilia americana.

[2] The southeastern portion of the ecoregion, along the border of Oaxaca and Chiapas, has a subhumid climate, and average annual rainfall of 1040-1600 mm per year.

Characteristic trees of the subhumid forests are plumajillo (Alvaradoa amorphoides), cacho de toro (Bucida macrostachya), brasil (Haematoxylum brasiletto), carnero (Coccoloba floribunda), mulato (Bursera simaruba), copalillo (Bursera bipinnata) and mezquite (Prosopis juliflora).