Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32 Page 33 Page 34 Page 35 Page 36 Page 37 Page 38 Page 39 Page 40 Page 41 Page 42 Page 43 Page 44 Page 45 Page 46 Page 47 Page 48 Page 49 Page 50 Page 51 Page 52 Page 53 Page 54 Page 55 Page 56 Page 57 Page 58 Page 59 Page 60Precipitation 16 When air masses encounter barriers like mountain ranges the air is forced up and over them in a process known as orographic lift. As air rises it cools and cannot hold as much water, so precipitation falls. This explains why Wyoming’s lowlands are dominated by shrubs and grasses, but its mountain environment supports trees such as conifers and aspens. Annual precipitation The threshold for growing most non-irrigated crops is 20 inches of precipitation per year. Most western states, including Wyoming, fall well below this average even during wet years. Droughts in Wyoming occur with some regularity. In 2012,Wyoming experienced its driest year on record with an increase in wildfires and economic hardship for the state’s ranchers and hay producers. Average annual total (1981–2010) Statewide average 16.2 inches Wet year total (1995) Statewide average 20.6 inches Drought year total (2012) Statewide average 11.1 inches Wyoming’s mountains: Islands of moisture January February March April May June July August September October November December Monthly average precipitation 1981–2010 (inches) < 0.5 1 2 3 4 > 5 Total annual precipitation (inches) 2 5 10 20 30 40 50 60 >70 Data Go Interactive