Accurate and reliable hourly rainfall data are crucial for hydrological analysis as inaccurate data induce misleading conclusions. This study assessed hourly rainfall data from Balai Besar Wilayah Sungai Ciliwung-Cisadane (BBWSCC) against daily records from Badan Meteorologi, Klimatologi, dan Geofisika Indonesia (BMKG). The analysis compared the rain occurrences, the accumulated annual rainfall, and the daily rainfall using statistical parameters: MSE, RMSE, MAE, and R2. The validation process indicated general disagreement, shown by high discrepancies and large errors. Notably, RMSE being approximately twice that of MAE suggested significant outliers, while negative R2 showed a lack of linear correlation. The errors did not correlate with station proximity. These findings highlighted the inconsistency between BBWSCC’s hourly rainfall data and BMKG’s daily records.