Say it gets to 20f 7c once a decade event while you are in bermuda for a week.
Water heater in garage cold weather.
And or the piping closest to the floor where in coming cold air will pool.
A water heater installed in the garage is often subjected to the same exterior temperatures as though it were setting outside.
When you request hot water by turning on a fixture it will pull water up from the main through the water heater where it warms the water and eventually through the plumbing system and out through your fixture.
If your water heater is in good working condition cold weather will not have an impact on temperature.
First choose between a gas or electric heater.
The cold pipe in or the hot pipe out fartherest from the hwh would be at greatest risk.
How cold would the unheated garage get.
As mentioned before cold weather can cause water heaters to work even harder especially if they are located in an unheated area.
Because water lines are chilled the water supply entering the hot water heater is much colder and requires more energy and longer recovery time.
If you notice that your energy bill is spiking more than usual during the winter months look to your water heater as the possible culprit.
Space out shower and bathroom times to allow the heater to bring the full tank of water up to the thermostat setting before placing more demand on the.
My concern is if there is any possibility of the pipes freezing.