Translation:Hali ya hewa
It may help to note that "hewa" can also mean air. So, "hali ya hewa" literally means "state of the air". Other languages also use this concept of "state of x" to mean the weather. Examples ,
Hava durumu - "state of the air" in Turkish , Umumo womkhathi - "state of the atmosphere" in northern Ndebele or Zulu, Maemero ekubanze - "state of the outside" in Ndau.
I hope that helps.