The drones' cameras cannot handle the sub-zero temperatures, a Ukrainian soldier, Ali, told the AFP news agency.
The batteries discharge faster, the cameras and cables freeze, they become completely iced over.
Both Ukrainian and Russian defenses rely on small, cheap drones to locate enemy positions, detect approaching attacks and to drop grenades. The recent cold snap, with temperatures dropping to minus 20 degrees, poses a major problem.
But old-fashioned solutions can come to the rescue. Grease can insulate the drones from the frost.
"We put lard on them and they take off," drone designer Denys Shtilierman told AFP.
