The wilderness area includes the volcano of the same name, over 400 hectares of volcanic ash and scoria, upland plateaus over 3, 000 meters above sea level, and small cloud forests that have been greatly altered by the eruptions of the volcano.

Apparently, the name Irazú is derived from “Istarú”, a 16^th century Indian palisade built on the southern slope above the existing village of Cot.

The climate on Irazú Volcano is cold and damp.  The average minimum temperatures are 48º C. But it can get as cold as –3º C (below freezing), when there are frequent frosts. Average annual rainfall is barely more than 2,000 mm., a small amount when compared to other regions in the country. During the dry season the sun shines brightly, the temperature is higher and visibility is excellent, affording views of the banks of fog beneath the giant volcano, the lush slopes of the Eastern Central Valley and the two oceans.