Spatial analysis of hydrological data often requires the interpolation of a variable from point samples. Commonly used methods for solving this problem include Inverse Distance Weighting (IDW) and Kriging (KG). IDW is easily extensible, has a competitive computational cost with respect to KG, hence it is usually preferred for this task. This paper proposes the optimization of finding the IDW parameter using a nature-inspired metaheuristic, namely Particle Swarm Optimization (PSO). The performance of the improved algorithm is evaluated in a complex scenario and benchmarked against the KG algorithm for 51 precipitation series from the Dobrogea region (Romania). Apart from facilitating the process of applying IDW, the PSO implementation for Optimizing IDW (OIDW) is computationally lighter than the traditional IDW approach. Compared to Kriging, OIDW is straightforward to be implemented and does not require the difficult process of identification of the most appropriate variogram for the given data.The interpolation method often chosen by geoscientists is IDW, implemented in many Geographic Information Systems (GIS) packages [4]. Its popularity is mainly due to its straightforward interpretability, easy computability and good prediction results. Still, the No Free Lunch theorem for optimization [5] stands also in the case of spatial interpolation: no method stands out as being the best in all situations [6]. In a study about the rainfall data in the Indian Himalayas, Kumari et al. [7] performed a comparison of several interpolation methods, among which there were several variants of multivariate Kriging and IDW. It was shown that none of the methods performs best in all the studied cases. Principal Component Regression with the Residual correction (PCRR) method, IDW and the Multiple Linear Regression (MLR) methods were used to compare interpolated annual, daily and hourly precipitation and the spatial distribution of precipitation in the Xinxie catchment [8], while the spatial distribution of precipitation deficit over Seyhan River basin using IDW is reported in [9].The basic IDW method is successfully employed in [10] to estimate the rainfall distribution in a region of Iraq. The scenario uses incremental values for the power parameter, in the range from 1 to 5. A modified IDW method is investigated in [11], where the elevation is also considered for estimating the values at unknown locations. A new method for estimating the regional precipitation (MPPM) has been introduced in [12] and its performance has been tested against that of IDW and kriging. It was reported that MPPM avoids the problems that could appear in the application of kriging methods, as (i) the invertibility of the distance matrix, (ii) the high computational cost related to building the inverse of the distance matrix in the case of a high number of stations, (iii) the choice of the model for the estimation of theoretical variogram and (iv) the selection of the optimal parameters of the variogram model. It was shown that deterministic methods could b...