Technologically there is no limitation to fly at night. Drone technology can work well the same as day. The visibility of the normal human eye can be restricted at night. Electronics, microwave, propagation of wave work same as day. In spite of the no limitations, we believe that this technology could be applied for emergency situations where light levels may not provide adequate illumination, preferably at night.
If the nature of the job is emergency in nature like food supply, medical items supply could be carried out at night. For example during a serious accident or disaster. Soon after any natural calamity, drones can supply foods and medicine well. There are plenty of houses around a particular area with a limited budget to produce foodstuffs quickly, as they were unable even to feed their children due to too much drinking water over time. So it’s important to use drones whenever possible since you’ll need them very soon after the disaster.
For hobby purpose, need to avoid flying at night. Because flying at night needs navigational light and anti-collision light. Both of them need to be assured.