I was about to leave when suddenly it rained.
我正要离开，就在这时突然下起雨来。
In the afternoon it rained suddenly.
下午天突然下雨了。
突然下起雨来。
Yesterday, I decided to go outside for picnic, but unfortunately, it suddenly rained.
昨天我决定去野炊，不幸的是突然下雨了，我感到很失望。
One day after school, it suddenly rained heavily.
一天放学后，突然下起了大雨。
We were about to go when it suddenly rained.
我们正要出发，突然天下雨了。
She bought an umbrella because it rained suddenly.
因为突然下起雨来，她买了把伞。
Because it rained suddenly, we cancelled the picnic yesterday.
昨天因为天突然下雨了，所以我们取消了野炊。
But unfortunately, when we was starting to hike, it suddenly rained.
但不幸的是，当我们到的时侯，正要准备出发，突然下起大雨来。
It was because it rained suddenly that we cancelled the picnic yesterday.
昨天因为天突然下雨了，所以我们取消了野炊。
It was because it rained suddenly that we cancelled the picnic yesterday.
昨天因为天突然下雨了，所以我们取消了野炊。
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