A phase change material (PCM) is used as thermal storage for lighting systems. The PCM is placed in a thermally conductive container in close contact with the lighting system. As the PCM absorbs heat, it changes from a solid to a liquid state, but the temperature of the PCM is clamped at its melting point temperature. For LED-based systems, the PCM is selected to have a melting point such that the junction temperatures of the LEDs in the system are maintained at approximately their optimum operating temperature inside the lighting system housing. Because the thermal conductivity of the molten PCM is poor, a low thermal resistance heat flow path is provided from the PCM to the container.