Lancaster has a cold semi-arid steppe climate . The area within Lancaster is covered by shrublands (80%), forests (8%), grasslands (7%), lakes and rivers (2%), and croplands (2%). Lancaster and its immediate surroundings are part of USDA Plant Hardiness Zone 8b. Winters are cool to mild, with daily normal minimum temperatures at or just below freezing from late November until late January, and the coolest month, December, having a normal mean temperature of 43.8 °F (6.6 °C). Summers are hot and nearly rainless, with July, the hottest month, having a normal mean temperature of 82.3 °F (27.9 °C). On average, annually there are 68 days with a minimum at or below freezing, and 30 days with a maximum at or above 100 °F (37.8 °C). With a normal annual rainfall of 7.38 inches (187 millimeters), clear days are the norm even in winter, when surrounding mountain ranges are blanketed with snow. Thunderstorms are infrequent but do occur in July through September. There is a mild frost throughout March, and temperatures begin to climb in April. Spring wildflowers are abundant, including Lupines, the California Poppy, Fiddlenecks, purple owl’s clover, California Goldfields, Creamcups, and Coreopsis. Summer nights are cool and the Pacific tree frog or barn owl can be heard. Average annual snowfall is around two inches (5 cm).
The record high temperature in Lancaster was 115 °F (46 °C) on June 30, 2013. The record low temperature was 2 °F (−17 °C) on December 24, 1984. The wettest year was 1983 with 29.83 inches (758 mm) and the driest year was 1953 with 1.26 inches (32 mm). The most precipitation in one month was 11.45 inches (291 mm) in February 1980. The most precipitation in one twenty-four- hour period was 2.93 inches (74 mm) on March 1, 1983. In December 1979, 23.9 inches (610 mm) of snow fell in Lancaster.