看来天气有些不稳定。

The weather looks slightly iffy.

《牛津词典》

举个极端的例子，以单一作物为主的农田是如此不稳定，一年的坏天气或单一害虫的入侵可以摧毁整个作物。

To take an extreme example, farmlands dominated by a single crop are so unstable that one year of bad weather or the invasion of a single pest can destroy the entire crop.

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即使天气好的时候，食盐供应也不稳定。

Even in fair weather, however, supplies can be unstable.

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