实测资料表明出现雾时，极端最小相对湿度是91%，在相对湿度低于90%的情况下，没有观测到雾。

The observational data show that the minimum relative humidity for fog to occur is 91%, and there is no fog when the relative humidity is lower than 90%.

youdao

实测资料表明出现雾时，极端最小相对湿度是91%，在相对湿度低于90%的情况下，没有观测到雾。

The observational data show that the minimum relative humidity for fog to occur is 91%, and there is no fog when the relative humidity is lower than 90%.

youdao