Split-flap displays show information using characters changed by an electric motor. While they’ve largely been replaced by more modern means, hobbyists like “gabbapeople” have been keeping this this technique alive, in this case as a four-character weather display.
The device is built using laser-cut plexiglass, and uses four individual servos to actuate the character flaps. Control is accomplished using an Arduino Mega programmed in the XOD visual programming environment, along with the requisite driver modules. Weather data is pulled from the AccuWeather API.
You can see it flapping away in the video below, displaying the weather in abbreviations such as “ICLO” for intermittent clouds, as well as the temperature in degrees Celsius.