For a long time I treated weather in the sim as background flavor – something the engine generated to make the sky look nice, not something I actually planned around. Then I started flying regularly on VATSIM, where the weather is pulled from real METAR data and controllers expect you to fly appropriate approaches for actual conditions, and I had to actually learn to read the raw reports instead of glancing at a “current conditions” icon. It’s less intimidating than it looks once you break it into pieces.
METAR: a snapshot, not a forecast
A METAR is a routine surface observation, issued roughly every hour (with special reports, or SPECIs, issued when conditions change significantly in between). It tells you what’s actually happening at an airport right now, not what’s expected later – that’s the TAF’s job. A typical string looks like this:
KJFK 271951Z 28014G22KT 10SM FEW035 SCT250 24/12 A3002 RMK AO2 SLP159
Read left to right: station identifier, then the day and time of observation in Zulu (UTC), then wind direction and speed with gusts if present, then visibility, then cloud layers, then temperature and dew point, then altimeter setting, then remarks. Once you’ve parsed a few dozen of these the pattern becomes automatic – the order never changes, only the values do.
The parts that actually change your flight
Wind is the first thing I check, because it decides which runway is in use and whether a crosswind approach is realistic for the aircraft you’re flying. 28014G22KT means wind from 280 degrees at 14 knots, gusting to 22. If that’s roughly perpendicular to your assigned runway, expect a bumpier approach and budget more control input on the flare.
Visibility and cloud layers together tell you whether you’re realistically flying visual or need to brief a full instrument approach. 10SM is ten statute miles – functionally unlimited for approach planning. FEW035 means a few clouds at 3,500 feet, and SCT250 means scattered clouds at 25,000 feet – neither is a ceiling that would force an instrument approach. If you instead see something like BKN006, that’s a broken ceiling at 600 feet, and now you’re briefing minimums and expecting to fly the approach in cloud, not just decorating the sim with mist.
Temperature and dew point (24/12) matter for performance calculations on hot days and for icing risk when they’re close together and near freezing. Altimeter setting (A3002, meaning 30.02 inches of mercury) needs to go into your altimeter before descent – flying a stale setting into a low-pressure system will put you lower than your instruments say, which is exactly the kind of error real procedures are built to prevent.
TAF: what to expect for your arrival
A Terminal Aerodrome Forecast covers a window of time, typically 24 to 30 hours, and shows how conditions are expected to change through that period using the same coded groups as METAR. This is the report you check before departure if your flight is long enough that conditions at the destination might shift meaningfully before you land.
TAFs use change groups – BECMG for a gradual transition, TEMPO for temporary fluctuations, FM followed by a time for an abrupt change – to show a forecast timeline rather than a single value. A TAF showing TEMPO 2008/2012 3SM -RA BR means that between 08:00 and 12:00 Zulu on the 20th, expect temporary drops to 3 miles visibility in light rain and mist. If your estimated arrival lands inside that window, that’s your cue to brief an instrument approach and pick a sensible alternate rather than assume the current fine weather will hold.
Where to pull real data
You don’t need to memorize every code group from a textbook – decode tools exist specifically so you can check your understanding against the plain-language translation while you’re learning. Aviation Weather Center is the authoritative US source and includes a decoder alongside the raw text. metar-taf.com covers airports worldwide with a clean side-by-side raw and decoded view, which is what I actually keep open in a browser tab during flight planning. The ICAO publishes the underlying format standards if you want the full reference rather than a working summary.
Why bother if the sim generates its own weather anyway
Modern simulators can pull live weather automatically, which is genuinely convenient, but reading the raw report yourself changes how you fly. You start briefing approaches based on actual ceiling and visibility instead of just loading whatever the engine renders. You notice a stiff crosswind before it surprises you on short final. And on any online network where controllers and other pilots are working from the same real-world data, understanding the report puts you on the same page as everyone else in the pattern – which, on a busy VATSIM event with fifteen aircraft inbound to the same runway, is exactly where you want to be.