Kinda off topic, but I once spoke with a guy who taught weather forecasting for the military. He explained that TV, cable, and radio don't hire forecasters for their skills - they hire them so that they will do OK if they are ever used in broadcast. In contrast, wars are won or lost based on weather forecasts - so the military invests like no one else in training their forecasters. He told me that if I want a decent forecast, I need to find out which government agency provides forecasts for a nation's airlines. They will be the only civilian organization investing in getting the good forecasters. (And I have found that to be true for the US - the National Weather Service (NOAA) consistently has better forecasts.) I know that this doesn't answer your question - but it seems like this isn't widely known, considering the horrible forecasts I routinely ignore from my phone, computer, and browser.

I like http://openweathermap.org/. They have historical data: http://openweathermap.org/history

Weather Underground (wunderground) has an API. It's free for limited usage: http://www.wunderground.com/weather/api/d/docs

Forecast.io is a pretty solid API used by many apps, built by the makers of Dark Sky.