Averiguando que tiempo hace

• http://openweathermap.org/: Call current weather data for one location
• OpenURI is an easy-to-use wrapper for Net::HTTP, Net::HTTPS and Net::FTP.

  Véase la Documentación

• JSON is a lightweight data-interchange format. It is easy for us humans to read and write. Plus, equally simple for machines to generate or parse. JSON is completely language agnostic, making it the ideal interchange format.
• Psych is a YAML parser and emitter. Psych leverages libyaml for its YAML parsing and emitting capabilities. In addition to wrapping libyaml, Psych also knows how to serialize and de-serialize most Ruby objects to and from the YAML format.

[~/rubytesting]$ cat wheater.rb 
require 'open-uri'
require 'json'
require 'psych'

city = 'san cristobal de la laguna,spain'.gsub(/\s/,'%20')
request = "http://api.openweathermap.org/data/2.5/weather?q=#{city}&units=metric"
response = open(request).readlines.join
print Psych.dump( JSON.parse(response) )

[~/rubytesting]$ pry
[1] pry(main)> require 'open-uri'
=> true
[2] pry(main)> require 'json'
=> true
[3] pry(main)> require 'psych'
=> true

[4] pry(main)> city = 'san cristobal de la laguna,spain'.gsub(/\s/,'%20')
=> "san%20cristobal%20de%20la%20laguna,spain"

[5] pry(main)> request = "http://api.openweathermap.org/data/2.5/weather?q=#{city}&units=metric"
=> "http://api.openweathermap.org/data/2.5/weather?q=san%20cristobal%20de%20la%20laguna,spain&units=metric"

[6] pry(main)> f = open(request)
=> #<StringIO:0x007fdee29fc4a0
 @base_uri=
  #<URI::HTTP:0x007fdee29fc720 URL:http://api.openweathermap.org/data/2.5/weather?q=san%20cristobal%20de%20la%20laguna,spain&units=metric>,
 @meta=
  {"server"=>"nginx",
   "date"=>"Tue, 07 Oct 2014 10:30:15 GMT",
   "content-type"=>"application/json; charset=utf-8",
   "transfer-encoding"=>"chunked",
   "connection"=>"keep-alive",
   "x-source"=>"redis",
   "access-control-allow-origin"=>"*",
   "access-control-allow-credentials"=>"true",
   "access-control-allow-methods"=>"GET, POST"},
 @metas=
  {"server"=>["nginx"],
   "date"=>["Tue, 07 Oct 2014 10:30:15 GMT"],
   "content-type"=>["application/json; charset=utf-8"],
   "transfer-encoding"=>["chunked"],
   "connection"=>["keep-alive"],
   "x-source"=>["redis"],
   "access-control-allow-origin"=>["*"],
   "access-control-allow-credentials"=>["true"],
   "access-control-allow-methods"=>["GET, POST"]},
 @status=["200", "OK"]>

[7] pry(main)> a = f.readlines
=> ["{\"coord\":{\"lon\":-16.31,\"lat\":28.49},\"sys\":{\"type\":3,\"id\":5518,\"message\":0.1935,\"country\":\"Spain\",\"sunrise\":1412665299,\"sunset\":1412707453},\"weather\":[{\"id\":803,\"main\":\"Clouds\",\"description\":\"broken
clouds\",\"icon\":\"04d\"}],\"base\":\"cmc
stations\",\"main\":{\"temp\":24,\"pressure\":1018,\"humidity\":73,\"temp_min\":24,\"temp_max\":24},\"wind\":{\"speed\":4.1,\"deg\":80},\"clouds\":{\"all\":75},\"dt\":1412674200,\"id\":2511401,\"name\":\"San Cristóbal de la Laguna\",\"cod\":200}\n"]