# aviationwheater.siten.co

> Independent aviation weather guides — 15 in this language — covering METAR and TAF decoding, in-flight hazards, regional briefing patterns and weather-based flight planning. Educational, not an operational source.

Contact: contactmail.bsam@gmail.com
Languages: en (https://aviationwheater.siten.co/), de (https://aviationwheater.siten.co/de), es (https://aviationwheater.siten.co/es), fr (https://aviationwheater.siten.co/fr), hi (https://aviationwheater.siten.co/hi), id (https://aviationwheater.siten.co/id), it (https://aviationwheater.siten.co/it), nl (https://aviationwheater.siten.co/nl), pl (https://aviationwheater.siten.co/pl), pt (https://aviationwheater.siten.co/pt), sv (https://aviationwheater.siten.co/sv), tr (https://aviationwheater.siten.co/tr)

## Guides (https://aviationwheater.siten.co/guides)

- [Crosswind and Runway Condition: Turning Wind Into a Number](https://aviationwheater.siten.co/guides/crosswind-and-runway-conditions): How to convert a reported wind into a crosswind component, what a demonstrated limit actually is, and why a wet runway lowers the usable figure. — Weather and flight planning, Updated 2026-08-09.
- [The Preflight Weather Briefing: A Checklist That Works](https://aviationwheater.siten.co/guides/preflight-weather-briefing-checklist): A briefing is a sequence, not a website. Here is the order that answers the route questions before the aerodrome ones, and the checks people skip. — Weather and flight planning, Updated 2026-08-09.
- [Weather Minimums: What VFR and IFR Actually Require](https://aviationwheater.siten.co/guides/weather-minimums-vfr-ifr): The difference between VFR and IFR is not skill, it is what the weather allows. Here are the visibility and cloud rules, and where the numbers come from. — Weather and flight planning, Updated 2026-08-08.
- [Winter Operations: De-icing, Holdover Times and Contaminated Runways](https://aviationwheater.siten.co/guides/winter-operations-and-de-icing): Why winter departures collapse into queues, what a holdover time really is, and how a runway condition code changes the numbers a crew has to meet. — Regional aviation weather, Updated 2026-08-08.
- [Monsoon and Tropical Aviation Weather: Flying the Wet Season](https://aviationwheater.siten.co/guides/monsoon-and-tropical-aviation-weather): What the monsoon actually does to flights, why tropical convection is a daily rather than seasonal problem, and how the reports read differently in the tropics. — Regional aviation weather, Updated 2026-08-08.
- [Aviation Weather by Region: What Each Part of the World Briefs For](https://aviationwheater.siten.co/guides/aviation-weather-by-region): The same aircraft meets a different set of problems in every part of the world. Here is what dominates each region, when, and which service publishes it. — Regional aviation weather, Updated 2026-08-07.
- [Turbulence: The Four Types, and Which Ones Can Be Forecast](https://aviationwheater.siten.co/guides/turbulence-types-and-forecasts): Clear-air, mechanical, convective and wake turbulence come from different causes and are predicted with very different success. Here is which is which. — Weather hazards in flight, Updated 2026-08-07.
- [Thunderstorms and Convective Weather: Why Aircraft Go Around Them](https://aviationwheater.siten.co/guides/thunderstorms-and-convective-weather): A cumulonimbus contains every serious weather hazard at once. Here is what is inside one, how far aircraft stay away, and why the avoidance is lateral. — Weather hazards in flight, Updated 2026-08-07.
- [Aircraft Icing Explained: Where It Forms, and Why It Is So Serious](https://aviationwheater.siten.co/guides/aircraft-icing-explained): Ice changes the shape of a wing, and a wing is only a shape. Here are the three types, the temperature band that produces them, and what the reports tell you in advance. — Weather hazards in flight, Updated 2026-08-06.
- [METAR and TAF Abbreviations: The Complete Decoder Table](https://aviationwheater.siten.co/guides/metar-taf-abbreviations): Every abbreviation you will meet in a routine report, grouped by where it appears — intensity, descriptor, phenomenon, cloud, trend and the runway groups. — METAR and TAF decoding, Updated 2026-08-06.
- [How to Read a TAF: Change Groups, Windows and Probability](https://aviationwheater.siten.co/guides/how-to-read-a-taf): A TAF is not a METAR for later. It is a forecast written in change groups — BECMG, TEMPO, PROB30 — and reading it means reading the transitions. — METAR and TAF decoding, Updated 2026-08-06.
- [How to Read a METAR: Every Field, in Order](https://aviationwheater.siten.co/guides/how-to-read-a-metar): A METAR is one line in a fixed order. Read it left to right and each group answers a different question — here is what each one says and what it decides. — METAR and TAF decoding, Updated 2026-08-05.
- [Where Aviation Weather Actually Comes From (and Which Sources Count)](https://aviationwheater.siten.co/guides/aviation-weather-sources): Which organisation issues the report you are reading, why only some sources are legally usable for a flight, and what the free apps are really showing you. — Aviation weather basics, Updated 2026-08-05.
- [How Weather Affects Flights: Delays, Diversions and Cancellations](https://aviationwheater.siten.co/guides/how-weather-affects-flights): Why a clear sky at your airport still produces a two-hour delay, what actually triggers a diversion, and which weather cancels a flight outright. — Aviation weather basics, Updated 2026-08-04.
- [What Is Aviation Weather? The Five Numbers That Decide a Flight](https://aviationwheater.siten.co/guides/what-is-aviation-weather): Aviation weather is the same atmosphere reported differently: cloud base in feet, visibility in metres, wind to ten degrees. Here is what each number decides, and why. — Aviation weather basics, Updated 2026-08-04.

## Topics (https://aviationwheater.siten.co/topics)

- [Aviation weather basics](https://aviationwheater.siten.co/topics/weather-basics): What aviation weather actually is, how a front turns into a delay or a diversion, and where pilots and dispatchers get the reports that decide it. — 3 guides.
- [METAR and TAF decoding](https://aviationwheater.siten.co/topics/metar-taf): How to read a METAR and a TAF field by field: wind groups, visibility, weather codes, cloud layers, temperature, QNH and the trend group, with the full abbreviation table. — 3 guides.
- [Weather hazards in flight](https://aviationwheater.siten.co/topics/flight-hazards): The weather that changes a flight: airframe and engine icing, thunderstorms and convective cells, clear-air and mountain-wave turbulence, low-level windshear and reduced visibility. — 3 guides.
- [Regional aviation weather](https://aviationwheater.siten.co/topics/regional-weather): Aviation weather is regional. Monsoon, harmattan dust, North Atlantic icing, Mediterranean crosswinds and typhoon season — what each part of the world briefs for and when. — 3 guides.
- [Weather and flight planning](https://aviationwheater.siten.co/topics/flight-planning): Turning a forecast into a decision: VFR and IFR minimums, the preflight briefing checklist, crosswind components, runway condition codes and alternate planning. — 3 guides.

## Aviation weather by region (https://aviationwheater.siten.co/regions)

- [North America](https://aviationwheater.siten.co/regions/north-america): Continental extremes in one airspace: summer squall lines across the Midwest, freezing rain and de-icing queues from November, and Pacific coastal fog that closes approaches on clear-looking mornings.
- [Western Europe](https://aviationwheater.siten.co/regions/western-europe): A maritime climate whose defining problems are visibility and wind rather than convection: radiation fog at inland hubs, autumn and winter gales that push crosswinds past limits, and low stratus that sits for days.
- [Northern Europe](https://aviationwheater.siten.co/regions/northern-europe): Long winters dominate the operation: contaminated runways, holdover-time arithmetic, freezing drizzle in the approach and daylight measured in hours rather than a whole working day.
- [The Mediterranean](https://aviationwheater.siten.co/regions/mediterranean): Terrain and sea meet to make wind the main story — mistral, bora, meltemi and the funnelled crosswinds of the Aegean — with autumn convection and Saharan dust arriving on the same southerly flow.
- [The Middle East](https://aviationwheater.siten.co/regions/middle-east): Heat and dust set the limits: performance-critical summer temperatures, blowing dust that drops visibility to a few hundred metres within minutes, and shallow overnight fog at coastal hubs.
- [South Asia](https://aviationwheater.siten.co/regions/south-asia): The southwest monsoon dominates half the year, with heavy rain, low ceilings and reduced visibility, while winter brings the dense radiation fog that regularly closes northern Indian airports at dawn.
- [Southeast Asia](https://aviationwheater.siten.co/regions/southeast-asia): Convection every afternoon rather than once a season: towering cumulonimbus, tropical cyclones from the Pacific, low-level windshear on approach and haze that closes airports for weeks in some years.
- [East Asia](https://aviationwheater.siten.co/regions/east-asia): Typhoon season, the strongest jet stream on the planet and the clear-air turbulence that comes with it, plus spring dust transported from the interior across busy northern approaches.
- [Oceania](https://aviationwheater.siten.co/regions/oceania): Mountain wave and rotor over the Southern Alps, roaring-forties wind at exposed coastal airports, summer convection over the Australian interior and morning fog in the southern basins.
- [South America](https://aviationwheater.siten.co/regions/south-america): The Andes generate wave and severe mechanical turbulence beside some of the world’s highest airports, while the subtropical plain produces intense summer convection and the region carries a live volcanic ash risk.
- [Africa](https://aviationwheater.siten.co/regions/africa): Harmattan dust reduces visibility across West Africa for months, the intertropical convergence zone drags a belt of severe storms north and south with the seasons, and coverage of the reports themselves varies by state.
- [The North Atlantic and Arctic](https://aviationwheater.siten.co/regions/north-atlantic): Long overwater legs with few alternates, persistent airframe icing in the climb and descent, rapidly deepening lows and an ash risk that has already closed the airspace once in living memory.

## Frequently asked questions

### What is aviation weather, and how is it different from an ordinary forecast?
Aviation weather is the same atmosphere reported in a different way, because flights care about different things than picnics do. A public forecast tells you it will be cloudy with a chance of rain. An aviation report tells you the cloud base in hundreds of feet, how much of the sky each layer covers, the visibility in metres or statute miles, the wind direction to the nearest ten degrees, the temperature and dew point, and the pressure setting to a hectopascal — because those five numbers decide whether an approach is legal, how much runway is needed, and whether ice will form on the wing. The two main products are the METAR, an observation of what is happening now, and the TAF, a forecast for a specific aerodrome over a fixed window.

### How do I read a METAR?
Left to right, in a fixed order: station identifier, day and time in UTC, wind as direction and speed, visibility, present weather, cloud layers from the lowest up, temperature and dew point, pressure, and finally a trend group. So EGLL 121250Z 24012KT 9999 FEW035 SCT120 14/09 Q1013 NOSIG reads as: Heathrow, on the 12th at 12:50 UTC, wind from 240° at 12 knots, visibility 10 km or more, a few clouds at 3,500 ft and scattered at 12,000 ft, 14 °C with a dew point of 9 °C, pressure 1013 hPa, no significant change expected. The decoder on our regions pages will do this for any report you paste, in your own language.

### What is the difference between a METAR and a TAF?
A METAR is an observation and a TAF is a forecast. The METAR describes conditions measured at the aerodrome, normally issued every half hour or hour, with a SPECI in between when something changes sharply. The TAF forecasts conditions in a defined area around the aerodrome for a period that is usually 24 or 30 hours, and it only mentions weather expected to be significant for operations. That is why a TAF looks sparser: it is written in change groups — BECMG, TEMPO, PROB30 — that describe what will alter and when, rather than painting the whole picture again.

### Which weather causes the most flight delays?
It depends on the season and the region, but four causes dominate. Thunderstorms close whole route segments and cause the largest en-route disruption, because cells are avoided laterally and a line of them can shut a corridor for hours. Low visibility and low ceilings reduce the arrival rate at busy airports, which builds delay across the network even when individual flights still land. Snow and ice add de-icing time to every departure and cut the number of movements the runway can take. Strong crosswinds slow arrivals and occasionally force a diversion. In most northern-hemisphere networks, winter contamination and summer convection account for the two annual delay peaks.

### Is this site an official weather source?
No, and it is important to be exact about that. We explain what aviation weather products contain and how to read them; we do not issue, relay or forecast anything. The authoritative source is the meteorological service designated by the state — the Aviation Weather Center in the United States, the Met Office and DWD in Europe, the IMD in India, REDEMET in Brazil, and so on — and each of our region pages links the relevant one. A flight must be planned on an official briefing, and the pilot in command is the only person who can decide whether it goes.

### How far ahead is aviation weather actually reliable?
Reliability drops sharply with time, and the useful horizon depends on the phenomenon. Wind and temperature at cruise level are reasonably good three to five days out. Frontal timing — when the rain or the wind shift arrives — is often uncertain by several hours even inside 24 hours, which is why a TAF is amended so frequently. Convection is the hardest: forecasters can say a region is likely to develop storms, but where an individual cell will stand at 16:00 is not knowable a day ahead, which is why the tools that matter for thunderstorms are radar and satellite in the last hours rather than a forecast made yesterday.