The mountain lies in an arid region and features a montane climate; estimated precipitation rises from at to at elevation mostly during summer, although rainfall might exceed . During the night the temperatures can fall to under . Grasses and shrubs with rare trees form the vegetation, mostly on the eastern flank and sometimes reaching high elevations. Among the plant species that grow in the area are yareta plants. The dry climate is caused by the South East Pacific High and compounded by the Humboldt Current off the coast, which cools the atmosphere and reduces evaporation. Only during the summer months does convection on the Bolivian Altiplano lead to the arrival of moisture, leading to a predominant summer precipitation. The climate becomes even drier farther south. Cut-off lows can sometimes reach Sillajhuay in winter but are uncommon. In the past, such as 28,000, 8,000 and 3,700 - 1,500 years ago the climate was more humid and this led frequently to glacier advances when it was also cold enough. In return, glaciers on Sillajhuay may have enhanced the moisture supply to other mountains in the area such as Chuquiananta, allowing them to develop glaciers as well. The strong insolation leads to a strongly diurnal temperature cycle on the mountain with a day-night temperature gradient of about that in some environments can increase to over ; there are thus active freeze-thaw cycles. The warming also leads to the development of mountain breeze and valley breeze, convective clouds as well as occasional landspouts. The summit of Sillajhuay can be climbed and features Inca ruins on the summit; there are a number of such high altitude ruins in the Andes such as at Llullaillaco. This site was discovered in 2013. Mining takes place east of Sillajhuay, including sulfur mines; estimated deposits are of ore with 47% sulfur. The area has also been prospected for the possibility of obtaining geothermal power. The whole volcano is considered to be of Pliocene-Pleistocene age, although the lack of detailed study precludes a precise dating of volcanic activity. The strong glacial modification implies that volcanism at Sillajhuay took place during the older Pleistocene. The maximum age of 730,000 ± 160,000 years is set by the age of the underlying ignimbrites although dates obtained directly on the volcanic rocks from Sillajhuay imply ages of as much as 2.47 ± 0.06 million years ago.