"Wow, Kona is humid!"
Translation:Hū ka ikiiki o Kona!
I could be wrong, but from what Iʻve learned so far, "ke" is only used before a word starting with k, e, a, or o.
For ' and for p, ka is standard, but ke is sometimes used. I think I've also seen ke used once with an h, so there may be other exceptions. But in general I believe you're right that it should be ke in front of k, e, a, and o and ka in front of other letters. And certainly in this sentence, before an i, ka is correct.