Project advice - Solar temp sensor fan controller

Hello,
It’s been a while (October 2016 was my last project), and I am back for more project advice and help. I am looking to install several (likely 4) of these (or something similar) roof fans -

The arduino part:-
I would like to have temp sensors under the eaves (likely 4-6) and temp sensors in the roof cavity (likely 4-6). When internal temp > eaves temp the fans would activate. When internal temp < eaves temp the fans shut down. The arduino would need to be powered by a solar panel (no point running the board if there is no power for the fans). Probably with a sensor read every hour or half hour.

It’s been a long time since I’ve used arduino but I am confident I could find a way to do it, but how would you (the experienced ones) do it?
How would you manage different temp readings?
would you include humidity, too?
Would you have it as a wired system, or wireless (I have no preference)?
The main part I’m not sure of - How would you tell the fans to run?

I look forward to your advice, thoughts, and input.

Regards,

Cup