In METAR reporting, what does the letter "X" represent?

In METAR reporting, the letter "X" signifies intense weather conditions or phenomena. In the context of METAR, this usage is often seen to indicate phenomena that are significantly impactful, such as heavy precipitation or severe weather conditions—situations that demand immediate attention from pilots and other aviation professionals. Recognizing this code is essential for understanding the severity of current weather and ensuring safety during flight operations.

While "X" can indicate intense conditions, other weather lexicons and codes serve to convey specific phenomena such as freezing rain, thunderstorms, or high winds—each with its own symbol or abbreviation. Thus, "X" stands out as an alert to pilots regarding more extreme weather that goes beyond ordinary thresholds, emphasizing the importance of keen situational awareness and proactive safety measures.