My very elderly (Electrolux) fridge worked just fine all through the hot weather. Temperatures of around 30 degrees outside (possibly higher inside the van at times), but the fridge stayed as cool as it should.
The freezer did get warmer than usual a couple of times, though. I noticed it getting as warm as -14 one day, even though the fridge was as cool as usual.
Of course the fridge is the bit with the thermostat, and the freezer is as cold as it needs to be to keep the fridge at temperature. So I'd expect a colder freezer in hot weather!