My husband lived on a farm in South Dakota, and remembers being told to read the propane % level for his grandpa. He read 20%. Then, there was a spell of extreme weather (he can't remember if it was extremely cold or warm for the time of year -- he was ten or eleven years old). That same day, all the pilot lights in the house went out. Grandpa was angry that Tim had read the gauge wrong. They checked it together, it read only 10%. As most of the other country, we are had a real cold spell, subzero temps, then 40F, now it's down below freezing again. Our propane tank right now reads 50%. It's about 30F now. What fluctuation of "real" propane volume can be expected? If at 30F we have 50%, if the temps dropped into the teens or lower, as they will, would the "volume" increase or decrease? Sounds weird, but is there a conversion factor?