Decoding an aviation METAR:

A standard METAR is written with the following variables:

{airport code} METAR {day}{time}Z {wind direction}{wind speed}KT {visibility}SM {precipitation} {cloud coverage}{elevation} {temperature (°C)}{dew point (°C)} A{barometric pressure at mean sea level} RMK AO2 {coded remarks}

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Here's an example of a Metar, it's different parts are listed in different colors:

KDTW METAR 141554Z 05005KT 3SM -SN BR OVC024 01/M02 A3013

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Here's the example METAR above decoded:

KDTW: The ICAO (4-Letter) airport code, in this case, Detroit;

14: The day of the month, in this case, the 14th;

1554Z: The 24H Zulu (UTC) time of the observation, in this case, 3:54PM Zulu;

050: Wind direction, in this case, wind blowing from the 050° radial (North East);

05KT: Wind speed in knots (adding "G##" after indicates a wind gust in knots);

3SM: Visibility in Statute Miles, in this case, 3 miles of visibility;

-SN BR: Precipitation indicators, in this case, light snow and mist;

OVC024: Cloud coverage and height (displayed as Feet X 100), in this case, overcast               skies at 2,400 feet;

01: Air temperature in °C, in this case 1°C;

M02: Dew point in °C (M standing for "minus"), in this case, -2°C

A3013: Altimeter setting (sea level pressure) in inHg, in this case, 30.13"Hg

All other text are remarks, and very depending on the weather conditions and type of weather station being used.

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CLOUD COVERAGE CODES

FEW: Few Clouds, 1/8 to 2/8 of clouds obstructing sky;

SCT: Scattered Clouds, 3/8 to 4/8 of clouds obstructing sky;

BKN: Broken Clouds, 5/8 to 7/8 of clouds obstructing sky;

OVC: Overcast Skies, 8/8 of clouds obstructing sky, completely cloud covered.

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PRECIPITATION CODES

Intensity Marks:

"-" = Light, "(blank)" = Moderate, "+" = Heavy, "VC" = In the Vicinity.

Descriptor Marks:

MI=Shallow, BC=Patches, BL=Blowing, TS=Thunderstorm, PR=Partial,

DR=Low Drifting, SH=Showers, FZ=Freezing.

Precipitation Marks:

RA=Rain, SN=Snow, IC=Ice Crystals, GR=Hail, DZ=Drizzle, SG=Snow Grains,

PL=Ice Pellets, GS=Snow Pellets, UP=Unknown Precipitation

Obstruction Marks:

FG=Fog, BR=Mist, DU=Widespread Dust, SA=Sand, VA=Volcanic Ash, HZ=Haze, FU=Smoke, PY=Spray

Other Marks:

SQ=Squall, DS=Duststorm, FC=Funnel Cloud, PO=Dust/Sand Whirls, SS=Sandstorm