Could be a lot of fuel related things. 20deg f is a little warm to be having fuel issues, but summer untreated fuel could be causing the fuel to plug the filter (Cold Filter Plugging Point). My notes say this can occur at between 10-15 f.
Start by thoroughly bleeding the fuel system. The procedure varies by machine type. If the problem continues, check fuel flow at several points from the tank out. If your machine has an electric lift pump, confirm that it is running with the key on. Finally, cracked or leaking fuel lines can suck air causing problems.