Call me crazy but I feel like my Orange Pi Zero decides to heat up or not randomly on every reboot. In the exact same place and env. temperature, only few minutes aparts and a reboot later it idles around either 40C or 50C depending on its mood.
Follow this page: http://www.armbian.com/kernel/
AFAIK these packages should be enough:
linux-image-dev-sun8i
linux-firmware-image-dev-sun8i
linux-dtb-dev-sun8i