Average annual rainfall ranges from 2000 to 4000 millimeters, with many areas experiencing regular heavy cloud cover.

On Tacaná, subalpine grasslands occur above a belt of Juniperus standleyi shrubs that define the treeline at about 4000 meters elevation.

The subalpine grasslands are dominated by Lupinus montanus and tussocks of the grass Calamagrostis vulcanica growing up to 1 meter high.

Other grasses and herbaceous plants include Alchemilla pinnata, Arenaria bryoides, Draba volcanica, Festuca tolucensis, Gentiana pumilio, Gnaphalium salicifolium, Haplopappus stolonifer, Lobelia nana, Luzula racemosa, Pernettya prostrata, Potentilla heterosepala, Viola nannei, Weldenia candida, and Werneria nubigena.

Other subalpine grasses include Bromus carinatus, Briza rotunda, Festuca amplissima, Muhlenbergia gigantea, M. macroura, M. robusta, Piptochaetium virescens, Stipa ichu, and Trisetum irazuense.