haze 是坏天气

fog, mist 是一种常见自然景象，成份是冷却后的水蒸气，
影响可视度，有时候身临其境有美感。

haze 是一种非正常气象现象，天气预报应该报道，不但
严重影响可视度，同时刺激呼吸道黏膜危害人体健康。

The following is also a copy and past from Internet,
通过成份、位置和可见度把云、雾和大雾给了比较好的解释。
If your head is in the clouds, it is probably really in the fog.
Unless its in the mist! The difference between fog, mist
and cloud is less to do with its constitution, and more to do
with its location.

The fog is really just a low lying cloud, although its definition
is determined by its effect on visibility.When visibility is between
1000 and 5000 metres it is refered to as mist.Sometimes fog
can become so thick it can reduce visibility to only a few metres.