明天要下雨的英语怎么说

明天要下雨的英语表达是 "It's going to rain tomorrow." 或 "Tomorrow is going to be rainy." 。

这种表达方式来源于英语中动词 "to be going to" 的用法。"To be going to" 表示将要发生的事情，它是一种将来时的表达方式。

例句1:
"It's going to rain tomorrow."
(明天要下雨。)

例句2:
"I think it's going to rain this afternoon."
(我认为今天下午要下雨。)

例句3:
"The weather forecast says it's going to be rainy tomorrow."
(天气预报说明天要下雨。)