I found this 'API' which returns the following data:
{
 "cidade":"Sao Paulo - SP",
 "agora":{
  "data_hora":"08\/11\/2013 - 19:59",
  "descricao":"Muito Nublado (noite)",
  "temperatura":"19",
  "humidade":"73%",
  "visibilidade":"9,99 km",
  "vento_velocidade":"20,92 km\/h",
  "vento_direcao":"SE",
  "pressao":"1.015,92 mBar",
  "pressao_status":"subindo",
  "nascer_do_sol":"6:16 am",
  "por_do_sol":"7:25 pm",
  "imagem":"http:\/\/developers.agenciaideias.com.br\/images\/tempo\/27.png"
 },
 "previsoes":[
  {
   "data":"Sexta - 08\/11\/2013",
   "descricao":"Parcialmente Nublado (noite)",
   "temperatura_max":"23",
   "temperatura_min":"16",
   "imagem":"http:\/\/developers.agenciaideias.com.br\/images\/tempo\/29.png"
  },
  {
   "data":"S\u00e1bado - 09\/11\/2013",
   "descricao":"Tempo Bom (dia)",
   "temperatura_max":"27",
   "temperatura_min":"18",
   "imagem":"http:\/\/developers.agenciaideias.com.br\/images\/tempo\/34.png"
  },
  {
   "data":"Domingo - 10\/11\/2013",
   "descricao":"Ensolarado",
   "temperatura_max":"29",
   "temperatura_min":"21",
   "imagem":"http:\/\/developers.agenciaideias.com.br\/images\/tempo\/32.png"
  },
  {
   "data":"Segunda - 11\/11\/2013",
   "descricao":"Parcialmente Nublado (dia)",
   "temperatura_max":"32",
   "temperatura_min":"23",
   "imagem":"http:\/\/developers.agenciaideias.com.br\/images\/tempo\/30.png"
  },
  {
   "data":"Ter\u00e7a - 12\/11\/2013",
   "descricao":"Parcialmente Nublado (dia)",
   "temperatura_max":"30",
   "temperatura_min":"19",
   "imagem":"http:\/\/developers.agenciaideias.com.br\/images\/tempo\/30.png"
  }
 ]
}
Follow the url:
http://developers.agenciaideias.com.br/tempo
I tested the request described in the documentation, with Angularjs, and returned everything straight.  =) 
							
							
						 
There are several widgets on the site of Climatempo and Tempo Agora. Gives a search.
– Diego
but I didn’t want something ready Diego, as I made clear in the question, I wanted to take the information via json for example, something similar as it is done in the post office, for later I manipulate and create my own widget, but I will take a look at these sites also to see how it is.
– DiChrist
"see if it can be solved in a similar way to that of the post office" - precisely, making a proper Rawler can be the way. You need to see if the site license allows it. " I can neither deny nor confirm" that I do this currently with a quality source, but somehow I quote the source in the final result, I imagine that I have no problems with the "license" in this way kkk.
– Bacco