I am working on a school project that includes both my raspberry pi and aruduino, I have made a temperature script that allows me to monitor the pi's current temperature and I am wondering if I can read this output from my arduino in order to control a fan's speed.
You can actually to it all with the Raspberry Pi. Control you fan with a PWM value that will then turn on and off a MOSFET.
If you really have to do it with the Arduino, the "simple noob" way of doing this is to send a PWM pulse output from the Pi and analog read it from the Arduino. From there, do the same as you would do with the Pi.