GRAFFAS model generates hourly rainfall fields from areal statistics. It can be applied on climatically diverse domains. More explanation about the model in Cantet et al 2024 : Space-time simulation of hourly rainfall from areal statistic published in Water Resources Research http://dx.doi.org/10.1029/2024WR038562. Here (in the GRAFFAS-v0.tar), codes for calibrating and running GRAFFAS are available. A dataset ( gridded hourly rainfall on Gapeau and Paris domains from COMEPHORE product) is provided to run codes (from calibration to simulation) in ./DATA folder. Note that COMEPHORE dataset (gridded hourly precipitation in continental France) is freely available in https://meteo.data.gouv.fr/datasets/669e23a7ce052a9e8521b75e. Codes are implemented in R. Mandatory packages are listed in ./InstallNeededPackages.r, this routine enables to install them. Codes were tested only on Lunix platform. Using Mac-OS and Windows should be ok. Nevertheless, Lunix platform is recommended to use correctly parallel::mclapply() function. File ./main.r calibrates and runs GRAFFAS model from the provided dataset (Gapeau domain). GRAFFAS parameters and simulation are saved in ./SAVE_STEP folder while simulations are stored in ./RRsim folder. All needed internal functions to run main.r are stored in ./FUNCTIONS folder.