Thanks Ioannis,

You're right: less than that is almost impossible

Now drive the raised GND of the LM35 to another ADC input of your PIC
I need to ADC measure the raised GND only once since it will never change - or am I missing something?

And "yes", for sure I'll have values to measure that will be below 0°C; in fact, they will have to be always under 0°C or I'll have a problem with the food inside the freezer