Let's talk about the weather

Recently, I had to quite thoroughly communicate with several services of Yahoo! In this article I will talk about one of them, which may be useful for many. This is Yahoo! Weather .

About two years ago I searched the network for a convenient and open source of such data, but I did not find anything. All domestic services exported data for money (it was not the price that scared off rather than having to pay), but Westerners either did not provide data in a convenient format for automatic processing, or did not know about the existence of the city in which I live.

Yahoo! Weather pleased with the absence of these shortcomings. Information about the current weather, as well as the forecast for the next 5 days is exported from their server in RSS format. In my opinion, the choice of this format is pulled by the ears, because weather RSS "feed" contains only one item. The same data could be exported in a more concise way, but Yahoo seemed to rely on standard RSS processing methods, which is also quite a weighty argument. Standard is still standard.
')
The RSS feed address for the city of interest can be found at weather.yahoo.com .



In general, the URL is as follows:

xml.weather.yahoo.com/forecastrss?p=_&u=_

The first parameter is the identifier of the city of interest. The second parameter determines in which units the temperature will be displayed. The value of "c" corresponds to degrees Celsius, "f" - degrees Fahrenheit.
A few examples:

• Moscow - http://xml.weather.yahoo.com/forecastrss?p=RSXX0063&u=c
• St. Petersburg - http://xml.weather.yahoo.com/forecastrss?p=RSXX0091&u=c
• Ekaterinburg - http://xml.weather.yahoo.com/forecastrss?p=RSXX1219&u=c
• Khanty-Mansiysk - http://xml.weather.yahoo.com/forecastrss?p=RSXX1234&u=c
• Kiev - http://xml.weather.yahoo.com/forecastrss?p=UPXX0016&u=c

Automate it

The YahooWeather class (PHP5) described below is designed to download RSS over HTTP and preprocess data.

  <? php

 class YahooWeather {
	 // Wind
	 public $ wind_chill;
	 public $ wind_direction;
	 public $ wind_speed;
	
	 // Atmospheric indicators
	 public $ humidity;
	 public $ visibility;
	 public $ pressure;
	
	 // We translate sunrise and sunset time to unix time
	 public $ sunrise;
	 public $ sunset;
	
	 // Current air temperature and weather
	 public $ temp;
	 public $ condition_text;
	 public $ condition_code;
	
	 // Weather forecast for 5 days
	 public $ forecast;
	
	 public $ units;
	
	 function __construct ($ code, $ units = 'c', $ lang = 'en') {
		 $ this-> units = ($ units == 'c')? 'c': 'f';
		
		 $ url = 'http://xml.weather.yahoo.com/forecastrss?p='.
			 $ code. '& u ='. $ this-> units;
		
		 $ xml_contents = file_get_contents ($ url);
		 if ($ xml_contents === false) 
			 throw new Exception ('Error loading'. $ url);
		
		 $ xml = new SimpleXMLElement ($ xml_contents);
		
		 // Wind
		 $ tmp = $ xml-> xpath ('/ rss / channel / yweather: wind');
		 if ($ tmp === false) throw new Exception ("Error parsing XML.");
		 $ tmp = $ tmp [0];
		
		 $ this-> wind_chill = (int) $ tmp ['chill'];
		 $ this-> wind_direction = (int) $ tmp ['direction'];
		 $ this-> wind_speed = (int) $ tmp ['speed'];
		
		 // Atmospheric indicators
		 $ tmp = $ xml-> xpath ('/ rss / channel / yweather: atmosphere');
		 if ($ tmp === false) throw new Exception ("Error parsing XML.");
		 $ tmp = $ tmp [0];
		
		 $ this-> humidity = (int) $ tmp ['humidity'];
		 $ this-> visibility = (int) $ tmp ['visibility'];
		 $ this-> pressure = (int) $ tmp ['pressure'];
		
		 // We translate sunrise and sunset time to unix time
		 $ tmp = $ xml-> xpath ('/ rss / channel / yweather: astronomy');
		 if ($ tmp === false) throw new Exception ("Error parsing XML.");
		 $ tmp = $ tmp [0];
		
		 $ this-> sunrise = strtotime ($ tmp ['sunrise']);
		 $ this-> sunset = strtotime ($ tmp ['sunset']);
		
		 // Current air temperature and weather
		 $ tmp = $ xml-> xpath ('/ rss / channel / item / yweather: condition');
		 if ($ tmp === false) throw new Exception ("Error parsing XML.");
		 $ tmp = $ tmp [0];
		
		 $ this-> temp = (int) $ tmp ['temp'];
		 $ this-> condition_text = strtolower ((string) $ tmp ['text']);
		 $ this-> condition_code = (int) $ tmp ['code'];
		
		 // Weather forecast for 5 days
		 $ forecast = array ();
		 $ tmp = $ xml-> xpath ('/ rss / channel / item / yweather: forecast');
		 if ($ tmp === false) throw new Exception ("Error parsing XML.");
		
		 foreach ($ tmp as $ day) {
			 $ this-> forecast [] = array (
				 'date' => strtotime ((string) $ day ['date']),
				 'low' => (int) $ day ['low'],
				 'high' => (int) $ day ['high'],
				 'text' => (string) $ day ['text'],
				 'code' => (int) $ day ['code']
			 );
		 }
	 }
	
	 public function __toString () {
		 $ u = "°". (($ this-> units == 'c')? 'C': 'F');
		 return $ this-> temp. '  '. $ u.', '. $ this-> condition_text;
	 }
 }

 ?> 

Example of use:

  <? php

 try {
	 $ weather = new YahooWeather ('RSXX0091');
 } catch (Exception $ e) {
	 echo "Caught exception:". $ e-> getMessage ();
	 exit ();
 }

 echo '<h1>'. $ weather. '</ h1>';

 echo "<pre>";
 print_r ($ weather);
 echo "</ pre>";

 ?> 

Conclusion:



Sunrise and sunset time values ​​(sunrise and sunset fields, respectively) are automatically converted to the unix time format. It should also pay attention to the fact that for some unknown reason, Yahoo! gives an obviously incorrect value of atmospheric pressure (0). But the very presence of the corresponding attribute in XML gives some hope that sooner or later the export of this data will be repaired.

The condition_code field is used to store the weather code code. The text decoding of the current value is stored in the condition_text field, and the full list of possible options is given in the following table:

Code	Description
0	tornado
one	tropical storm
2	hurricane
3	severe thunderstorms
four	thunderstorms
five	mixed rain and snow
6	mixed rain and sleet
7	mixed snow and sleet
eight	freezing drizzle
9	drizzle
ten	freezing rain
eleven	showers
12	showers
13	snow flurries
14	light snow showers
15	blowing snow
sixteen	snow
17	hail
18	sleet
nineteen	dust
20	foggy
21	haze
22	smoky
23	blustery
24	windy
25	cold
26	cloudy
27	mostly cloudy (night)
28	mostly cloudy (day)
29	partly cloudy (night)
thirty	partly cloudy (day)
31	clear (night)
32	sunny
33	fair (night)
34	fair (day)
35	mixed rain and hail
36	hot
37	isolated thunderstorms
38	scattered thunderstorms
39	scattered thunderstorms
40	scattered showers
41	heavy snow
42	scattered snow showers
43	heavy snow
44	partly cloudy
45	thundershowers
46	snow showers
47	isolated thundershowers
3200	not available

The article was published on the paradigm.ru blog.

Related Links

• Yahoo! Weather
• Yahoo! Weather RSS feed @ Yahoo! Dev Network - a complete description of the exported data