Does anyone know, if there's a site with precipitation (amount of rain in mm/inches) history for different cities? I need the data of Helsinki, Finland. I'm currently using Dark Sky Forecast API to get the current precipitation levels, but it doesn't seem to support that with history calls.
I'll cache the current values as they come, but can't get old data. I can update the database manually as a one off if I can get the data.
Weather Underground has free historical data. Here's data for Helsinki from January 1, 2015 through June 18, 2015 (for example). You can customize the data range and manually download as a CSV file.