后天去野餐用英文怎么说

"Going on a picnic after tomorrow" 的英语表达方式是 "going on a picnic the day after tomorrow"。

"After tomorrow" 这个词组来源于英语中的时间表达方式。在英语中，"tomorrow" 是 "明天" 的意思，"after tomorrow" 就是 "后天" 的意思。

下面是一些英文例句：

I'm going on a picnic the day after tomorrow. (我后天去野餐。)
We're planning to go on a hike the day after tomorrow. (我们计划后天去远足。)
He's going to visit his grandparents the day after tomorrow. (他后天要去拜访他的祖父母。)