If you’re looking for global precipitation data, the german weather service (Deutscher Wetterdienst) is one of the top addresses. On their portal you will find a huge amount of rainfall data, in some cases you can get time series starting in 1901.
Besides a regional-based data selection, it’s possible to download complete worldwide precipitation datasets. With this datapower it’s easy to create diagrams and much more punctual related to your interests. To save time, the site offers a visualization tool which can be used for free.
All in all a nice datasource as a starting point for modeling and visualisation of precipitation issues.