This dataset presents the stable water isotopic composition (δ¹⁸O and δ²H) of daily precipitation collected in north-western Croatia (near Samobor town). A total of 288 precipitation samples were collected between December 2022 and November 2024, covering a period of two years. Each sample represents precipitation accumulated over a 24-hour period, with collection typically performed in the early morning. A RAIN SAMPLER RS1B, manufactured by Palmex, was used for sample collection. This rain gauge is specifically designed to collect and store precipitation samples while preventing post-collection evaporation.Stable isotope analyses of hydrogen and oxygen were conducted using a Picarro L2130-i Isotope Analyzer, providing analytical precisions of ±1‰ for δ²H and ±0.2‰ for δ¹⁸O. The isotopic values are expressed in δ-notation (‰), normalized to the Vienna Standard Mean Ocean Water (VSMOW) international reference standard. For each sample, the deuterium excess (d-excess) was calculated as: d-excess = δ²H – 8 × δ¹⁸O. The Local Meteoric Water Line (LMWL) was determined from the dataset after data screening. Specifically, 31 samples with negative or <1‰ d-excess values and 36 samples with precipitation amounts below 0.2 mm were excluded from the LMWL calculation due to potential evaporative enrichment. The resulting dataset was used to examine the primary climatic and moisture-source controls on the isotopic composition of precipitation in Croatia, as reported in the research article: "Assessing the influence of climatic parameters and moisture sources on precipitation isotope composition from central Croatia: Insights from a two-year long daily-resolved dataset." Beyond this publication, the dataset provides a valuable resource for hydrogeological, hydrological, climatological, and environmental applications, including isotope-based water balance studies, moisture source tracing, and regional climate variability assessments.

Sampling frequency: Daily (24-hour accumulation)Sampling method: Precipitation collected over 24-hour period using a PALMEX rain collector to prevent evaporation. Collection typically performed in the early morning around 07:00:00Number of samples: 288-Instrument(s):Picarro L2130-i Isotope AnalyzerPALMEX rain collector (evaporation-suppressing design)HOBO Rain Gauge Data Logger-Precision:±1 ‰ for δ2H±0.2 ‰ for δ18O-Data processing / Quality control: The isotopic dataset was filtered to ensure data quality prior to LMWL construction. Samples with negative or <1‰ d-excess values (n = 31) and precipitation amounts < 0.2 mm (n = 36) were excluded from regression analysis.-Normalization standard:Vienna Standard Mean Ocean Water (VSMOW)