An exemplary light emitting diode street lamp includes a light emitting diode array, a brightness sensor, a humidity sensor, and a controlling system. The brightness sensor senses the brightness of the environment. The humidity sensor senses the humidity of the environment. The controlling system is electrically connected to the light emitting diode array, the humidity sensor and the brightness sensor. Three ranges of humidity and three ranges of brightness are predefined in the controlling system. The controlling system controls the light emitting diode array to emit an amount of light according to a relationship between the sensed humidity value and the humidity ranges, and according to a relationship between the sensed brightness value and the brightness ranges.