Thank you so much for your responses. As you said, it may be better to rely HFR values than temperature but, as I have a temperature sensor, I say to myself: "hey, why not adding an additional focus trigger?". In fact, I'm autofocusing every 'x' minutes/shots and on filter change. And as I try to intercalate S2, Ha and O3 frames to get a full color image each night (weather just sucks here), maybe I'm just focusing too much. However, I'll explore the possibility to acquire the EAF probe if an opportunity arises.
Regarding to humidity, I was aware about some people complains about the PegasusAstro sensor but I don't have too much experience with the Powerbox yet. What I saw in the last 3 nights is that humidity was ramping from 60% to 97-99%... BUT weather was awful and it seems right. I'll check in the future who it behaves.
So, as conclusion, NINA doesn't allow to use the weather temperature to trigger the autofocus routine (at least at this moment).