in the visitor center. Climate Average precipitation, limited by the rain shadow effects of the Cascade Range and the Ochoco Mountains, varies from a year. In winter, much of the precipitation arrives as snow. Weather data for the city of Mitchell, near the Painted Hills Unit, show that July and August are the warmest months, with an average high of and an average low of . January is the coldest month, when highs average and lows average . The highest recorded temperature in Mitchell was in 1972, and the lowest was in 1983. May is generally the wettest month, when precipitation averages . Biology Flora More than 80 soil types support a wide variety of flora within the monument. These soils stem from past and present geologic activity as well as ongoing additions of organic matter from life forms on or near the surface. Adapted to particular soil types and surface conditions, these plant communities range from riparian vegetation near the river to greasewood and saltgrass on the alluvial fans to plants such as hedgehog cactus in rocky outcrops at high elevation. Important to many of these communities is a black cryptobiotic crust that resists erosion, stores water, and fixes nitrogen used by the plants. The crust is composed of algae, lichens, mosses, fungi, and bacteria. Other areas of the monument have little or no flora. Volcanic tuffs and claystones that lack essential nutrients support few microorganisms and plants. Likewise, hard rock surfaces and steep slopes from which soils wash or blow away tend to remain bare. Native grasses thrive in many parts of the monument despite competition from medusahead rye, Dalmatian toadflax, cheatgrass, and other invasive species. Bunchgrasses in the park include basin wildrye, Idaho fescue, Thurber's needlegrass, Indian ricegrass, and bottlebrush squirreltail, among others. Native grasses that form sod in parts of the monument include Sandberg's bluegrass and other bluegrass species. Reed canary grass, if mowed, also forms sod along stream banks. Limited by their need for water, trees such as willows, alders, and ponderosa pines are found only near the monument's streams or springs. Serviceberry bushes and shrubs like mountain mahogany are found in places where moisture collects near rock slides and ledges. Elsewhere long-rooted rabbitbrush has adapted to survive in dry areas. Other shrubs with adaptive properties include greasewood, sagebrush, shadscale, broom snakeweed, antelope bitterbrush, and purple sage. Western junipers, which have extensive root systems, thrive