The abbreviation ‘WX’ for weather has its roots in the world of telegraphy. In the late 19th and early 20th centuries, Morse code was widely used for sending messages over long distances. In Morse code, the letter ‘W’ is “.–” and ‘X’ is “-..-“. When put together, ‘WX’ became a quick and efficient way to denote ‘weather’ in coded messages.

Today WX is limited to mostly meteorological uses, basically a shorthand like “BRB” in electronic communication. Some weather websites use it too, mainly because most good.com web addresses with the word “weather” in them have long since been scooped up by others.