the average annual air temperature is about 48 degrees f and the average annual precipitation is 22 inches. due to its high storage of water that is plant available no irrigation is needed during the growing season to sustain at least three months of perennial grasses ranging from tall, mid, or short species. the amount of precipitation is sufficient to provide good production of organic residues but not enough to cause severe weathering and leaching. the climate and vegetation have interacted in south dakota to produce seven major soil regions. these regions are named: cool moist forest; cool, very dry plain; warm, very dry plain; cool dry plain; warm dry plain; cool moist prairie; and warm moist prairie.