"Yes, the vog has cleared."
Translation:ʻAe, mao ka polalauahi.
The past tense would be noted by the word ua before the verb mao, which, yes, is the same as ua meaning rain.
The action that's happening always goes at the beginning of the phrase. If the vog is clearing, then "mao" goes at the beginning. If someone is eating, then "'ai" goes at the beginning of the phrase. If someone is going, then "hele" goes at the beginning of the phrase. Many words can also be used as adjectives describing the kind of thing and those go after the thing they are describing. So "a hot day" is "He lā wela". If "mao" can be used as an adjective, then "ka polalauahi mao" would be something like "the cleared vog".