From the manual: the ideal range is 55 - 80 degrees F.
Danger zone: below 40 degrees F or above 90 degrees F.
The bin does come with a primitive heater. It is just
a piece of plywood wrapped with tinfoil and lines with
wires that heat up when you plug the unit in. There
is no thermostat, so you have to plug and uplug the
unit for any effect. Said plywood sheet wrapped in
tinfoil is supposed to have insulating properties for
heat and cold, so you are always supposed to leave it
on top of the compost pile, below the lid. I found
this to be a big nuisance and I didn't really need it
so I quit using it altogether, so far with no ill
effects.