Weather API, Python or JavaScript

Question 1

Once you have installed pywapi with pip, open a ipython shell and explore what pywapi can do. Here's an example which actually gives you what you want:-

In [1]: import pywapi

In [2]: pywapi.
pywapi.GOOGLE_CITIES_URL                   pywapi.YAHOO_WEATHER_URL                   pywapi.get_weather_from_weather_com        pywapi.urlopen
pywapi.GOOGLE_COUNTRIES_URL                pywapi.getText                             pywapi.get_weather_from_yahoo              pywapi.wind_beaufort_scale
pywapi.NOAA_WEATHER_URL                    pywapi.get_cities_from_google              pywapi.minidom                             pywapi.wind_direction
pywapi.URLError                            pywapi.get_countries_from_google           pywapi.quote                               pywapi.xml_get_attrs
pywapi.WEATHER_COM_URL                     pywapi.get_everything_from_yahoo           pywapi.re                                  pywapi.xml_get_ns_yahoo_tag
pywapi.YAHOO_WEATHER_NS                    pywapi.get_weather_from_noaa               pywapi.sys                                 pywapi.yield_all_country_city_codes_yahoo

In [2]: pywapi.get_weather_from_yahoo?
Type:       function
String Form:<function get_weather_from_yahoo at 0x10daeb9b0>
File:       /Users/calvin/.virtualenvs/myweather/lib/python2.7/site-packages/pywapi.py
Definition: pywapi.get_weather_from_yahoo(location_id, units='metric')
Docstring:
Fetches weather report from Yahoo! Weather

Parameters:
  location_id: A five digit US zip code or location ID. To find your location ID,
  browse or search for your city from the Yahoo! Weather home page (http://weather.yahoo.com/)
  The weather ID is in the URL for the forecast page for that city. You can also get
  the location ID by entering your zip code on the home page. For example, if you
  search for Los Angeles on the Weather home page, the forecast page for that city
  is http://weather.yahoo.com/forecast/USCA0638.html. The location ID is USCA0638.

  units: type of units. 'metric' for metric and '' for non-metric
  Note that choosing metric units changes all the weather units to metric,
  for example, wind speed will be reported as kilometers per hour and
  barometric pressure as millibars.

Returns:
  weather_data: a dictionary of weather data that exists in XML feed.
  See http://developer.yahoo.com/weather/#channel

In [3]: pywapi.get_weather_from_yahoo('USCA0638')
Out[3]:
{'astronomy': {'sunrise': u'6:16 am', 'sunset': u'7:28 pm'},
 'atmosphere': {'humidity': u'67',
  'pressure': u'1013.7',
  'rising': u'1',
  'visibility': u'16.09'},
 'condition': {'code': u'33',
  'date': u'Sat, 20 Apr 2013 9:46 pm PDT',
  'temp': u'18',
  'text': u'Fair',
  'title': u'Conditions for Los Angeles, CA at 9:46 pm PDT'},
 'forecasts': [{'code': u'31',
   'date': u'20 Apr 2013',
   'day': u'Sat',
   'high': u'26',
   'low': u'15',
   'text': u'Clear'},
  {'code': u'32',
   'date': u'21 Apr 2013',
   'day': u'Sun',
   'high': u'26',
   'low': u'14',
   'text': u'Sunny'},
  {'code': u'34',
   'date': u'22 Apr 2013',
   'day': u'Mon',
   'high': u'22',
   'low': u'13',
   'text': u'Mostly Sunny'},
  {'code': u'30',
   'date': u'23 Apr 2013',
   'day': u'Tue',
   'high': u'21',
   'low': u'14',
   'text': u'Partly Cloudy'},
  {'code': u'30',
   'date': u'24 Apr 2013',
   'day': u'Wed',
   'high': u'19',
   'low': u'13',
   'text': u'Partly Cloudy'}],
 'geo': {'lat': u'34.05', 'long': u'-118.23'},
 'html_description': u'\n[![][5]][5]<br />\n<b>Current Conditions:</b><br />\nFair, 18 C<BR />\n<BR /><b>Forecast:</b><BR />\nSat - Clear. High: 26 Low: 15<br />\nSun - Sunny. High: 26 Low: 14<br />\nMon - Mostly Sunny. High: 22 Low: 13<br />\nTue - Partly Cloudy. High: 21 Low: 14<br />\nWed - Partly Cloudy. High: 19 Low: 13<br />\n<br />\n<a href="http://us.rd.yahoo.com/dailynews/rss/weather/Los_Angeles__CA/*http://weather.yahoo.com/forecast/USCA0638_c.html">Full Forecast at Yahoo! Weather</a><BR/><BR/>\n(provided by <a href="http://www.weather.com" >The Weather Channel</a>)<br/>\n',
 'link': u'http://us.rd.yahoo.com/dailynews/rss/weather/Los_Angeles__CA/*http://weather.yahoo.com/forecast/USCA0638_c.html',
 'location': {'city': u'Los Angeles', 'country': u'US', 'region': u'CA'},
 'title': u'Yahoo! Weather - Los Angeles, CA',
 'units': {'distance': u'km',
  'pressure': u'mb',
  'speed': u'km/h',
  'temperature': u'C'},
 'wind': {'chill': u'18', 'direction': u'0', 'speed': u'0'}}

As you can see in the results, you can get the weather icon in html_description (http://l.yimg.com/a/i/us/we/52/33.gif) and the temp. Since the results returned to you is everything, you will need to extract/access it like you would do with a python dictionary.

UPDATE

Go to http://weather.yahoo.com/ and type in your zip code (or your city).
If there is more than one choice, pick the one you want.
Locate the link "extended forecast" under "6-10 day" column. Click it.
Look at the URL address bar and the numbers there is your city's zip code.

ALL CITY CODE

Here's the function that helps you get all country, city codes

In [4]: pywapi.yield_all_country_city_codes_yahoo?
Type:       function
String Form:<function yield_all_country_city_codes_yahoo at 0x10daebaa0>
File:       /Users/calvin/.virtualenvs/myweather/lib/python2.7/site-packages/pywapi.py
Definition: pywapi.yield_all_country_city_codes_yahoo(country_code, cities)
Docstring:
Yield all cities codes for a specific country.

Parameters:
  country_code: A four letter code of the necessary country. For example 'GMXX' or 'FRXX'.
  cities: The number of cities to yield

Returns:
  country_city_codes: A generator containing the city codes

Question 2

You can use Metwit weather api.
If you can implement them client-side: 200 request/day (ip based throttling) no authentication required. Worldwide coverage, JSON and REST compliant. You can register for extra API calls for free and if you still need it to call them server side the basic plan is pretty cheap.

Here a little example in jQuery: http://jsbin.com/isukam/1 that use our weather resource.

Full disclosure: I own this sweet piece of API.