It is fine sand.

这是细砂。

I'm going out in my chair in a day or two if it is fine.

过一两天，如果天气好的话，我就要坐着轮椅出去。

If it is fine tomorrow, we will go.

如果明天是晴天，我们就去。

If it is fine tomorrow, we can go out.

如果明天天气好，我门可以出门。

If it is fine tomorrow, we must go out.

如果明天天气好，我门必须出门。