This makes them very sensitive to temperature. If the ambient temperature is below 25 C, the absolute maximum rating is 30 mA. This current is a deadline and cannot be used. If the ambient temperature is between 25 C and 80 C, the current that can be used decreases rapidly. The temperature 80 C is the limit of useable temperature. Under this temperature, the LEDs cannot work even at 0 mA. In some cities, the ambient temperature is very high in summer time.
High temperature can cause inconsistency in the luminosity and chromaticity of an LED display.
High temperatures also dramatically shorten the life span of the LEDs. When they get too hot, LEDs cannot function properly, which may bring severe damage to the entire display. Further more, according to the feature of a semiconductor device, the voltage drop of it will decrease and the current will increase. This will make the condition even worse. Keep in mind that ambient temperature does not only refer to the temperature of the surrounding air.