If you can store your emergency water inside, this is ideal as it will protect it against environmental factors, especially during winter.
You can prevent your water from freezing if you create an underground water storage facility below the frost line. The ground will insulate the water, helping it stay above freezing point.
Unlike a plastic tank, a steel tank can absorb heat from the sun and retain it long enough to keep your water warm enough that it doesn’t freeze overnight.
You can increase the temperature inside your greenhouse by establishing a compost heap or open-top bin inside.
Livestock owners have been using this trick for years, but it only works on smaller containers due to the size of the tires. A standard car tire, for instance, is designed to fit a 15-inch wheel, so it will only protect a container of the same size.
Wrapping your tank in blankets or newspapers can help insulate the water and stop it from freezing. You could even use old mylar blankets, bearing in mind that these expire after a couple of years.
A standard-sized cooler can hold around 20 liters of water, which will keep a family of four hydrated for five days.