As shown here, the effect of temperature on the performance of fluorescent lamps is important. Rated lumen output values are obtained when measured at 77°F ambient temperature. Light output is a function of the mercury vapor pressure controlled by the coolest point on the bulb wall. Changes in ambient temperatures are accompanied by similar changes in bulb wall temperatures. For example, a drop of 10°F produces approximately a 10°F change in bulb wall temperature.
Because of the changes in light output with temperature, selection of the proper lamp for the application temperature range is an important one. Energy saving lamps should be operated in ambient temperatures of 60°F or higher. At lower temperatures, or with cold air hitting the lamps, flickering may occur or the lamp will simply put out less light.