Propane tanks will freeze up when the ambient temperature drops below -44°F. This is because propane has a boiling point of -44°F. If the temperature is not greater than -45°F, your propane will not vaporize, and your tank will freeze. However, as the temperatures drop, and the volume of propane in your tank drops, as will your pressure. If you do not have a heating source, it is important to keep your propane tank as full as possible at all times, to avoid freezing.
Another situation that can cause a propane tank to freeze up is pressure rate. Drawing more pressure than your tank is designed for, or pulling large amounts of pressure in a short amount of time.
You can prevent your tank from freezing by keeping it full, which means filling your tank more often. Or, you can look into heating systems. When researching ways to heat propane, safety is key. Try to find a heating method with safe heat, such as a heating blanket, or an insulated blanket, depending upon the amount of pressure needed. It is important to know how many watts are necessary to obtain the PSI levels desired or required. If it is not possible to calculate this yourself, you will want to look for a solution that can provide that information for you before you make the investment.
It is always important to remember when searching for a solution, to avoid open flames. Propane is a highly flammable gas and heating it can be extremely dangerous. Also avoid products that are not temperature controlled, overheating a propane tank can cause the pressure valve to blow, which will create a leak in your tank.