The rain that a grassland needs to survive for a year 草原生长所需的年降雨量

33. The young twins will now begin the nomadic life
    这两只小羊即将与其他草原动物一样
34. they share with most animals on the world's open plains.
    开始辽阔草原上不断迁徙的生活
35. Grasslands occur where rain is too sporadic for forests to exist.
    降雨量不足以养育森林时就会出现草原
36. The rain that a grassland needs to survive for a year
    草原生长所需的年降雨量
37. might arrive all at once.
    可能会一次来临
38. Storms like these can release 12 inches of rain in 24 hours.
    这样的暴雨在二十四小时内能达到三百毫米降雨量
39. Not much fun if you're out in it.
    淋起来可不好受

来自《行星地球 第二季 第五集 Planet Earth S02E05 草原》第 36 行