spring weather is unpredictable, with stormy, wet days being common, mixed with occasional warm, sunny weather. precipitation is normally heaviest in march. spring wildflowers bloom from april through june, peaking in may. fall days are usually clear and mild; nights are often cool. summer days are hot (), but overnight lows are usually comfortable (). afternoon thunderstorms are common from mid-july through mid-september. storms may produce waterfalls as well as flash floods. autumn tree-color displays begin in september in the high country; in zion canyon, autumn colors usually peak in late october. winter in zion canyon is fairly mild. winter storms bring rain or light snow to zion canyon and heavier snow to the higher elevations. clear days may become quite warm, reaching ; nights are often . winter storms can last several days and make roads icy. zion roads are plowed, except the kolob terrace road which is closed when covered with snow. winter driving conditions last from november through march.