Open Weather Map

https://openweathermap.org/current

  Access current weather data for any location including over 200,000 cities
  Current weather is frequently updated based on global models and data from more than 40,000 weather stations
  Data is available in JSON, XML, or HTML format
  Available for Free and all other paid accounts

https://api.openweathermap.org/data/2.5/weather?q=Bucharest&mode=html&appid=e12e3e492edfabe1f7ec11593a60253a

https://openweathermap.org/forecast5

  5 day forecast is available at any location or city
  5 day forecast includes weather data every 3 hours
  Forecast is available in JSON and XML
  Available for Free and all other paid accounts

https://openweathermap.org/forecast16

  16 day forecast is available at any location or city
  16 day forecast includes daily weather
  Forecast is available in JSON and XML
  Available for all paid accounts

https://openweathermap.org/history

  Through our API we provide city historical weather data for 37,000+ cities
  Historical data is available for 1 month previous in Starter account, for 1 year previous in Medium accounts, and for 5 years in History Bulk

https://openweathermap.org/history-bulk

  We have recently launched History Bulk functionality that provides weather data for 37,000+ cities.
  Historical data is available for 5 years and Pricing is simple and easy - just $10 for one city, no matter how much data will you receive.

http://openweathermap.org/api/weathermaps

  Weather maps include precipitation, clouds, pressure, temperature, wind, and more
  Connect our weather maps to your mobile applications and websites
  Use as layers in Direct Tiles, OpenLayers, Leaflet, and Google Maps
  Available for Free and all other paid accounts

https://openweathermap.org/api/uvi

  Current UV index (Clear Sky) and historical data are available for any geo location (lat/lon)
  Interpreting of the UV Index and recommended protection are provided
  Data is available in JSON
  Available for Professional and Enterprise accounts

https://openweathermap.org/stations

  API for managing your personal weather stations
  Creation of the station and measurements transfer
  Receiving the aggregated measurements from the station
  Available for Free and all other paid accounts

https://openweathermap.org/bulk

  We provide number of bulk files with current weather and forecasts
  Current weather bulk is available for 20,000 cities
  Variety of hourly and daily forecast bulks depends on frequency of data updating
  Available for Professional and Enterprise accounts

https://openweathermap.org/triggers

  Simple syntax to create triggers which will be working upon the occurrence of specified weather conditions (temperature, humidity, pressure, etc.) in a certain period of time.
  The alerts will be generated in our service after performing conditions of the trigger.

https://openweathermap.org/api/pollution/co - https://openweathermap.org/api/pollution/o3 - https://openweathermap.org/api/pollution/so2 - https://openweathermap.org/api/pollution/no2

  We provide current and historical (since November 2015) data on air pollution with main indexes of CO, O3, NO2 and SO2.
  Air pollution: ways to forecast and calculate it