[JRTJH]

Propane turns to a gas at very low temperatures but it slows down significantly at temperatures below about 20F. The less propane in the tank, the less liquid that will turn into gas and flow to the regulator. Next is the regulator, probably the most "sensitive" part of the system. Any water vapor in the regulator can cause it to stop flowing propane in the gas form. So, if the regulator gets "iced up" (something that happens in high humidity on cold nights) it may stop the flow of propane in the line to your appliances. That's why we're asking if the stove/water heater were operating normally. The water heater, as sourdough said, can be operated on electricity or propane (or both) and the tank will stay hot for several hours after propane stops flowing, so having hot water to wash your hands may not be an indication of anything not working properly on the propane side of the water heater. That's why I asked if the stove was operational.

Keep in mind that when you get back to the trailer this afternoon, if the sun has warmed the regulator, you may find that everything operates normally and will continue to do so, until the temperature falls again. The next time (hopefully it won't happen) but.... the next time the furnace stops working, try to determine if you have propane flow to the stove burners. If you do, then you have a furnace problem, probably the circuit board, but, on the other hand, if you can't light a stovetop burner, it's probably a problem with the propane flow, possibly the regulator.