How long does it take for sepsis to occur? is it related to hypothermia?my dad died a day after being exposed to 17-degree weather for 9 hours.

Its a process: Sepsis can occur swiftly (hours) when/if bacteria that elaborates destabilizing chemicals enter the bloodstream. A persons system may be handling an infection for a time up until their immune barriers fail & the spiral into sepsis & death can be rapid. You can become septic at high/ medium or low temperatures. The stress of low temperature could have pushed this beyond a salvageable point.