This paper analyzes linkages between lithic (lithobiontic, lithophytic) cyanobacterial community (LCC) abundance and climate across a wide range of environmental conditions and geographical distance in China's northwest region, an area containing some of the world's oldest, driest and most isolated deserts. In situ monitoring and long-term climate data show that extreme heterogeneity in liquid water availability characterizes the LCC environment across multiple spatial and temporal scales, with rainfall and snowmelt being the main moisture sources. Mean annual precipitation (MAP) primarily dictates LCC ecology across sites, but the interacting effects of temperature, moisture and light create a gradient of soil liquid water (ALW, 505--1839 hr yr-1) and conditions suitable for metabolic activity (200--922 hr yr-1) that also correlate with LCC abundance (0.99 1 0.2% to 12.6 1 1.8%). In situ soil temperatures indicate a minimum range of thermal tolerance for LCC in China's deserts of -23.80C to 53.80C. Through a comparison of similar available climate data for other deserts, we conclude that from a microbial physiological standpoint, although the hyperarid core of the Atacama Desert represents the driest nanoclimate environment recorded and the Dry Valleys in Antarctica represent the coldest desert conditions, it is the high-altitude deserts in the Qinghai-Tibetan Plateau that offer the coldest and driest recorded extremes for LCC on Earth.