Recently, Peters et al. (Phys. Rev. Lett. 88 (2002) 018701)) have found power-law behaviour in the distribution of rain events. Here it is shown that the observed self-similar features in both the reservoir level and the distribution of rain events, can quantitatively be reproduced from an extension to two dimensions of the Oslo-model developed to describe the dynamics of a pile of rice. Furthermore, it is argued that the sandpile model may be able to reproduce more detailed features such as the shape of cumulus clouds. In addition, many other systems, which show self-similarity in their time variations with the same quantitative characterizations, are discussed.