The warmer the temperature of curing epoxy, the faster it cures. The temperature of curing epoxy is determined by the ambient temperature plus the exothermic heat generated by its cure.
Ambient temperature is the temperature of the air or material in contact with the epoxy. Air temperature is most often the ambient temperature unless the epoxy is applied to a surface with a different temperature. Generally, epoxy cures faster when the air temperature is warmer.
Exothermic heat is generated by the chemical reaction that cures epoxy. The amount of heat produced depends on the thickness or exposed surface area of mixed epoxy. In a thicker mass, more heat is retained, causing a faster reaction and more heat. The mixing container's shape and the mixed quantity have a great effect on this exothermic reaction. A contained mass of curing epoxy (8 fl. oz. or more) in a plastic mixing cup can quickly generate enough heat to melt the cup and burn your skin. However, if the same quantity is spread into a thin layer, exothermic heat is dispersed, and the epoxy's cure time is determined by the ambient temperature. The thinner the layer of cured epoxy, the less it is affected by exothermic heat, and the slower it cures.