A practical alternative to getting the min/max thermometer to monitor freezer temps is to simply place a handful of frozen ice cubes in a sealed plastic baggy or other covered container.

As long as the power remains on and the fridge/freezer is properly operational, the ice cubes will remain intact. If the power is lost or the fridge/freezer has a malfunction the ice cubes will start melting when their temp reaches 0+C or 32+F.

You can also make a reasonably educated guess as to how long the power was off by looking at the amount of melting of the ice cubes in instances where the power was offline for several hours and was subsequently restored, thus preventing all the ice cubes melting.

If you come back and find that the ice cubes melted and have the resultant liquid has been refrozen in the shape of the container, then you are reasonably sure that the food in the fridge/freezer may have issues and should be considered as suspect for consumption.

We started doing this as a regular activity after coming back from vacation and finding that the house had a power loss. We ended up tossing all the food (composted some, fed some to the dogs) since we were unsure about it's status due to various neighbors providing conflicting information about the length of the power outage.

The utility company was not much help regarding questions about the length of the power outage, they just said that x number of customers had been without power and could not provide detailed enough information regarding locations and durations for our comfort.

Regards,
Comanche7