When people are having a picnic, but it begins to rain, they will be so sure about something that shows the weather is going to be fine very quickly.

当人们正在野餐，但开始下雨时，他们会非常肯定地认为天气会很快好起来。

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Rosy morning clouds indicate rain, and a rosy sunset means fine weather.

早霞主雨，晚霞主晴。

《新英汉大辞典》

Yes, the weather forecast. the forecaster said on the one hand it might be fine but on the other hand there might be some rain.

是的，天气预报，预报员说，一只手可能是晴天，另一只手可能会下雨。

youdao

But the fine weather is set to continue during the first part of the weekend, although rain is a real possibility on Saturday night and during Sunday.

BBC: Warm start for Glastonbury