Elevations in the park range from 800 feet to 6,643 feet and topography affects local weather. Temperatures are 10 to 20 degrees cooler on the mountaintops. Annual precipitation averages 65 inches in the lowlands to 88 inches in the high country. Spring often brings unpredictable weather, particularly in higher elevations. Summer is hot and humid, but more pleasant in higher elevations. Fall has warm days and cool nights and is the driest period, and frosts occur starting in late September. Winter is generally moderate, but extreme conditions occur with increasing elevation.