What does the remarks section of a METAR report always start with?

The remarks section of a METAR report always begins with "RMK." This is the standard abbreviation used in aviation meteorological reporting to indicate that what follows consists of additional or clarifying information related to the weather observation. This section can contain various types of information, such as significant weather phenomena, operational notes, or other relevant data that are not included in the main body of the METAR report.

Understanding this format is crucial for interpreting METAR reports accurately, as it ensures that pilots and meteorologists can quickly identify supplementary information that may affect flight operations or weather assessments. The use of a consistent abbreviation like "RMK" helps maintain clarity and brevity in meteorological communications.