Refiners alter the composition of fuel (petrol) to suit the time of year. More lighter elements to aid in atomization during the winter, less lighter elements during the summer to prevent vapour lock in the fuel lines. I can't for the life of remember the formulae right now, but it seems you attempted to use summer formulated fuel in too cold a temperature. The whole thing is based upon the 'Reed Vapour Pressure Test'. I'm sure a short search in Google will provide you a good link.
Regards,
W.B.