Both the SafeDip and the SaltDip displays have liquid crystal displays (LCD) much like today’s TVs and cell phones. The storage of the SafeDip and SaltDip would need to follow the same lines. You do not want to leave these items in an outside storage area where it will drop below freezing (32°F). If you do leave your tester in freezing temperatures, you need to transition the unit to a safe temperature SLOWLY. DO NOT immediately take it from freezing to a hot location such as the inside of a house, or a car with the heat running.
LCD generally recover as they warm up and will operate normally afterward. However, if you let the crystal freeze, you can damage or permanently alter the characteristics of the LCD display. The SafeDip and SaltDip are not intended for low-temperature use. Exposure to low temperatures can create bubbles or lead to permanent damage to the screen.
So in colder temperatures, keep it is best to keep the SafeDip & SaltDip units indoors.