AEMET API Integration

The Agencia Estatal de Meteorología (AEMET) provides free access to Spanish weather data through their OpenData API. This guide shows you how to integrate AEMET weather data into your PHP applications.

About AEMET OpenData

AEMET OpenData provides:

Real-time weather observations
Weather forecasts for Spanish locations
Historical climatological data
Weather station inventory
Meteorological warnings and alerts

You need a free API key to access AEMET OpenData. Register at opendata.aemet.es

Getting Started

Request Your API Key

Visit AEMET OpenData and create an account

Generate API Key

Navigate to your profile and generate a new API key

Store Securely

Save your API key in a secure configuration file (never commit to version control)

// claves.inc.php
<?php
$keyAEMET = "your_api_key_here";

Never expose your API key in public repositories. Use environment variables or separate configuration files that are excluded from version control.

Basic AEMET API Request

Here’s a complete example that retrieves the inventory of weather stations:

<?php

// https://opendata.aemet.es/centrodedescargas/ejemProgramas?

$curl = curl_init();

// Load API key from secure file
include("../../claves.inc.php");

curl_setopt_array($curl, array(
  CURLOPT_URL => "https://opendata.aemet.es/opendata/api/valores/climatologicos/inventarioestaciones/todasestaciones/?api_key=" . $keyAEMET, 
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "GET",
  CURLOPT_HTTPHEADER => array(
    "cache-control: no-cache"
  ),
));

$response = curl_exec($curl);
$err = curl_error($curl);
curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

API Endpoint Structure

AEMET API URLs follow this pattern:

https://opendata.aemet.es/opendata/api/{category}/{endpoint}?api_key={your_key}

Common Endpoints

Endpoint	Description
`/prediccion/especifica/municipio/diaria/{codigo}`	Daily forecast for a municipality
`/observacion/convencional/todas`	Current observations from all stations
`/valores/climatologicos/inventarioestaciones/todasestaciones`	Weather station inventory
`/prediccion/provincial/{provincia}`	Provincial weather forecast
`/avisos_cap/ultimoelaborado/{area}`	Latest weather warnings

Municipality codes can be found in the AEMET documentation. For example, Vigo’s code is 36057.

Two-Step Data Retrieval

AEMET API uses a two-step process:

Request Data URL

First request returns metadata and a temporary URL to the actual data

$response = curl_exec($curl);
$metadata = json_decode($response, true);

Fetch Actual Data

Use the datos URL from the metadata to get the actual weather data

if (isset($metadata['datos'])) {
  $dataUrl = $metadata['datos'];
  
  curl_setopt($curl, CURLOPT_URL, $dataUrl);
  $weatherData = curl_exec($curl);
  
  $stations = json_decode($weatherData, true);
}

Complete Example: Weather Forecast

<?php

function getAEMETForecast($municipalityCode, $apiKey) {
  $curl = curl_init();
  
  // Step 1: Get data URL
  $url = "https://opendata.aemet.es/opendata/api/prediccion/especifica/municipio/diaria/" . $municipalityCode;
  $url .= "?api_key=" . $apiKey;
  
  curl_setopt_array($curl, array(
    CURLOPT_URL => $url,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_TIMEOUT => 30,
    CURLOPT_CUSTOMREQUEST => "GET",
    CURLOPT_HTTPHEADER => array("cache-control: no-cache"),
  ));
  
  $response = curl_exec($curl);
  $err = curl_error($curl);
  
  if ($err) {
    curl_close($curl);
    return array('error' => $err);
  }
  
  $metadata = json_decode($response, true);
  
  // Check for API errors
  if ($metadata['estado'] != 200) {
    curl_close($curl);
    return array('error' => $metadata['descripcion']);
  }
  
  // Step 2: Get actual forecast data
  curl_setopt($curl, CURLOPT_URL, $metadata['datos']);
  $forecastResponse = curl_exec($curl);
  curl_close($curl);
  
  return json_decode($forecastResponse, true);
}

// Usage
include("claves.inc.php");
$forecast = getAEMETForecast("36057", $keyAEMET); // Vigo

if (isset($forecast['error'])) {
  echo "Error: " . $forecast['error'];
} else {
  print_r($forecast);
}

Debugging AEMET Requests

When developing, use debugging options to inspect the API communication:

<?php

$curl = curl_init();

include("../../claves.inc.php");

curl_setopt_array($curl, array(
  CURLOPT_URL => "https://opendata.aemet.es/opendata/api/valores/climatologicos/inventarioestaciones/todasestaciones/?api_key=" . $keyAEMET, 
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "GET",
  CURLOPT_HTTPHEADER => array(
    "cache-control: no-cache"
  ),
));

// Enable debugging options
curl_setopt($curl, CURLOPT_CERTINFO, true);
// curl_setopt($curl, CURLOPT_VERBOSE, true); // Uncomment for very detailed output

$response = curl_exec($curl);
$err = curl_error($curl);

// Display transfer information
var_dump(curl_getinfo($curl));

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

Understanding curl_getinfo() Output

The curl_getinfo() function returns useful debugging information:

array(
  'url' => 'https://opendata.aemet.es/...',
  'content_type' => 'application/json',
  'http_code' => 200,
  'header_size' => 487,
  'request_size' => 156,
  'total_time' => 0.742,
  'namelookup_time' => 0.012,
  'connect_time' => 0.098,
  'pretransfer_time' => 0.347,
  // ... more fields
)

Handling API Responses

Response Structure

AEMET API responses follow this structure:

{
  "descripcion": "exito",
  "estado": 200,
  "datos": "https://opendata.aemet.es/opendata/sh/...",
  "metadatos": "https://opendata.aemet.es/opendata/sh/..."
}

Processing Station Data

$response = curl_exec($curl);
$metadata = json_decode($response, true);

if ($metadata['estado'] == 200) {
  // Fetch actual data
  curl_setopt($curl, CURLOPT_URL, $metadata['datos']);
  $dataResponse = curl_exec($curl);
  
  $stations = json_decode($dataResponse, true);
  
  // Process each station
  foreach ($stations as $station) {
    echo "Station: " . $station['nombre'] . "\n";
    echo "Province: " . $station['provincia'] . "\n";
    echo "Coordinates: " . $station['latitud'] . ", " . $station['longitud'] . "\n\n";
  }
}

Error Handling

Implement robust error handling for production applications:

function safeAEMETRequest($url, $apiKey) {
  $curl = curl_init();
  
  curl_setopt_array($curl, array(
    CURLOPT_URL => $url . "?api_key=" . $apiKey,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_TIMEOUT => 30,
    CURLOPT_CUSTOMREQUEST => "GET",
  ));
  
  $response = curl_exec($curl);
  $err = curl_error($curl);
  $httpCode = curl_getinfo($curl, CURLINFO_HTTP_CODE);
  
  curl_close($curl);
  
  // Check for cURL errors
  if ($err) {
    return array(
      'success' => false,
      'error' => 'Connection error: ' . $err
    );
  }
  
  // Check HTTP status
  if ($httpCode >= 400) {
    return array(
      'success' => false,
      'error' => 'HTTP error: ' . $httpCode
    );
  }
  
  // Parse JSON
  $data = json_decode($response, true);
  
  if (json_last_error() !== JSON_ERROR_NONE) {
    return array(
      'success' => false,
      'error' => 'JSON parse error: ' . json_last_error_msg()
    );
  }
  
  // Check AEMET API status
  if (isset($data['estado']) && $data['estado'] != 200) {
    return array(
      'success' => false,
      'error' => 'API error: ' . $data['descripcion']
    );
  }
  
  return array(
    'success' => true,
    'data' => $data
  );
}

Rate Limits and Best Practices

AEMET API has rate limits. Excessive requests may result in temporary blocking.

Best Practices

Cache responses - Store weather data locally to reduce API calls
Implement retry logic - Handle temporary failures gracefully
Use appropriate timeouts - Set reasonable timeout values (30 seconds)
Respect rate limits - Add delays between consecutive requests
Store API keys securely - Never hardcode or commit API keys

Example: Simple Caching

function getCachedWeather($municipalityCode, $apiKey, $cacheTime = 3600) {
  $cacheFile = "cache/weather_" . $municipalityCode . ".json";
  
  // Check if cache exists and is fresh
  if (file_exists($cacheFile) && (time() - filemtime($cacheFile)) < $cacheTime) {
    return json_decode(file_get_contents($cacheFile), true);
  }
  
  // Fetch fresh data
  $weather = getAEMETForecast($municipalityCode, $apiKey);
  
  // Cache the result
  if (!isset($weather['error'])) {
    file_put_contents($cacheFile, json_encode($weather));
  }
  
  return $weather;
}

Additional Resources

AEMET OpenData Documentation

Official API documentation and examples

Weather APIs

Compare with other weather APIs

Next Steps

Now that you understand AEMET integration, explore other weather APIs:

OpenWeatherMap - Global weather data with more detailed forecasts
Open-Meteo - Free weather API with no API key required
Custom integrations - Combine multiple weather sources

Get Started

PHP Fundamentals

Database Programming

Session Management

Web Services

AJAX & Jaxon

API Integration

Assignments & Exams

AEMET API Integration

AEMET API Integration

About AEMET OpenData

Getting Started

Request Your API Key

Basic AEMET API Request

API Endpoint Structure

Common Endpoints

Two-Step Data Retrieval

Complete Example: Weather Forecast

Debugging AEMET Requests

Understanding curl_getinfo() Output

Handling API Responses

Response Structure

Processing Station Data

Error Handling

Rate Limits and Best Practices

Best Practices

Example: Simple Caching

Additional Resources

AEMET OpenData Documentation

Weather APIs

Next Steps

Get Started

PHP Fundamentals

Database Programming

Session Management

Web Services

AJAX & Jaxon

API Integration

Assignments & Exams

​AEMET API Integration

​About AEMET OpenData

​Getting Started

​Request Your API Key

​Basic AEMET API Request

​API Endpoint Structure

​Common Endpoints

​Two-Step Data Retrieval

​Complete Example: Weather Forecast

​Debugging AEMET Requests

​Understanding curl_getinfo() Output

​Handling API Responses

​Response Structure

​Processing Station Data

​Error Handling

​Rate Limits and Best Practices

​Best Practices

​Example: Simple Caching

​Additional Resources

AEMET OpenData Documentation

Weather APIs

​Next Steps

AEMET API Integration

About AEMET OpenData

Getting Started

Request Your API Key

Basic AEMET API Request

API Endpoint Structure

Common Endpoints

Two-Step Data Retrieval

Complete Example: Weather Forecast

Debugging AEMET Requests

Understanding curl_getinfo() Output

Handling API Responses

Response Structure

Processing Station Data

Error Handling

Rate Limits and Best Practices

Best Practices

Example: Simple Caching

Additional Resources

Next Steps