SkyDrill

Meaning of the M prefix in METAR temperatures

Remote Pilot (Part 107) practice question 5 of 18 on Weather / Sources. ACS element UA.III.A.K1 · difficulty: standard. Want to answer it in a timed quiz? Use the Remote Pilot (Part 107) practice mode.

Question bank updated 2026-09-22

QUESTIONA METAR temperature and dew point group reads M03/M05. What does this group indicate?

  1. ATemperature 3 °C and dew point 5 °C, measured at an automated station
  2. BTemperature −3 °C and dew point −5 °C
  3. CTemperature −3 °F and dew point −5 °F
Show the answer and explanation

Correct answer: B. Temperature −3 °C and dew point −5 °C

  • A — incorrect The M prefix indicates a minus value, not an automated measurement; an automated report is shown by the AUTO modifier.
  • B — correct Temperature and dew point are always given in degrees Celsius, and values below 0 °C are preceded by the letter M to indicate minus.
  • C — incorrect METAR temperatures are reported in degrees Celsius, never Fahrenheit.

BACKGROUND

In a METAR, the air temperature and dew point are always given in degrees Celsius, separated by a slash (for example 18/17). Temperatures below 0 °C are preceded by the letter M to indicate minus. This group follows the sky condition and precedes the altimeter setting in the report sequence. The temperature and dew point spread is one of the elements a remote pilot uses when judging local conditions before flight.

STUDY TIP

Treat M as a minus sign and remember the units are always Celsius. Do not confuse M (minus) with AUTO (automated source) or COR (corrected).

KEY POINTS

  • METAR temperature and dew point are always in degrees Celsius.
  • An M before a value means the temperature is below 0 °C.
  • The group is written as temperature/dew point, such as 18/17 or M03/M05.

SOURCES

  • remote_pilot_study_guide.txt, Chapter 3a "Aviation Routine Weather Report (METAR)", item 9 Temperature and dew point
Practice the Remote Pilot (Part 107) test →Timed 60-question exam, by ACS area, or review your misses. Free.
MORE ON WEATHER / SOURCES

SkyDrill is not affiliated with the FAA. This is an original practice item based on 14 CFR part 107, 14 CFR part 89, and the FAA Remote Pilot – Small UAS Study Guide (FAA-G-8082-22). Regulations and handbooks are revised; confirm details against the current edition.