onset of Meiyu

例句：

1. 1. The onset of spring is marked by the blooming of flowers.
   春天的到来标志着花朵的盛开。
2. 2. The onset of the disease was sudden and severe.
   疾病的发作突然且严重。
3. 3. The onset of winter is marked by the falling of leaves.
   冬天的到来以树叶的落下为标志。