Turn it off and leave the lid open during those months.

This appears to be about fridge-freezers, which have an extra level of complication.

Cheap and nasty fridge freezers have no independent control of temperature in the fridge and freezer compartments. They have one thermostat, in the fridge compartment, which switches the compressor on and off to cool both fridge and freezer. If the ambient temperature is, say, 20C, the difference between fridge and external temperature is 15 degrees, and the compressor will operate to maintain this. The difference between freezer and should be 38C and the system is designed to keep it that way.

Now, if external temp drops to 10 degrees, there is only a 5 degree difference between that and the fridge, which means that heat only gets in at a third of the rate. The compressor will therefore only operate for a third of the time it did at 20 degrees, to maintain the fridge temperature as before.

However, the difference between outside and freezer temperature has not dropped by the same proportion - it's still 28 degrees, and 28/38 is about 2/3. This means that the compressor should be running about two thirds of the time it did at 20 degrees. Result: temperature rises in freezer.

This is why fridge-freezers with one thermostat are a nasty compromise. They will use more energy than necessary to maintain a maximum freezer temperature over a range of room temperatures, and the temperature in the freezer will vary. Spend a few quid more on a proper one.

Chest freezers such as this do not have this complication.

I recently bought a freezer for our garage and after much searching the only ones I found suitable are Beko.
This taken from their product description
"Beko's innovative Freezer Guard technology ensures that this appliance will continue to function if the ambient temperature outside the freezer falls below zero or even as low as -15° Celsius, making this an ideal choice of appliance for locations such as garages or outbuildings"

ah, well in that case, here you go...

You can still use it all year round, but it will use more electricity in colder or hotter temperatures. The same may well be true for many freezers. There's not much you can do about it, they're just letting you know the efficiency decreases outside of it's optimal operating temperatures.

Good find...tempted!!

Quote from user manual: "...This unit can be used in a garage or outbuilding. For optimum energy efficiency the unit should be located within an average room temperature of between 10°C and 43°C. If the room temperature drops below or rises above these temperatures the energy consumption and performance may be affected..."

Which means it is unsuitable for use in a garage or outbuilding for 6 months of the year here(central Scotland).

Turn it off and leave the lid open during those months.

​surely if you were able to do without this for 6 months of the year, then you don't really need it in the first place.

been considering one of these for the garage, but no good if I can't use it half the year.

I recently bought a freezer for our garage and after much searching the only ones I found suitable are Beko.
This taken from their product description
"Beko's innovative Freezer Guard technology ensures that this appliance will continue to function if the ambient temperature outside the freezer falls below zero or even as low as -15° Celsius, making this an ideal choice of appliance for locations such as garages or outbuildings"

I have a norfrost been in my shed for at least 5 years never any problems

doesn't say it cannot be used in those conditions.