Propanes boiling point is -46f. As that temp. is neared, little vapor will be produced, resulting in low pressure. Understand that the liquid chills as the demand on it increases, so the liquid becomes colder than the ambient temp. Physics pressure dynamics 101.
It is common in the deep south and Mexico to blend butane into propane. Butane has a higher boiling point temp., thus production of vapor/ pressure is reduced at colder temps. It just cannot vaporize fast enough or at all to meet your demand.
Refill up north with pure propane, I bet your issue goes away.
