The aim to this paper was to estimate trends of hydrometeorological variables in a different time scales in order to see whether it will generate different conclusions and if there is an indication of the impact of climate change in the wider research area. Trends were estimated on a monthly and yearly basis for precipitation, air temperature, evapotranspiration and maximum water available for infiltration at meteorological station Pleso, and for Bregana River water levels at hydrological station Koretići. Both locations are important because they can show patterns that could be characteristic for the wider Zagreb area, and are associated with Zagreb aquifer recharge. Linear regression and t-test were used for trend estimation. Monthly analysis showed ascending trends for air temperature and evapotranspiration, especially in the summer months. Descending trends for Bregana River water levels were observed when minimum and average values were considered, while statistically significant ascending trend for maximum water levels was observed only for February. Yearly trends showed similar patterns. Also, it was shown that evaluation of trends only on a yearly basis can sometimes hide important information. All results suggest that more dry periods should be expected, while floods could be more frequent in February. Although not statistically significant, bigger difference between high and low waters, i.e. extremes, was observed. Trends showed that smaller infiltration from precipitation and reduced inflow from Bregana River to Sava River will probably result with the smaller recharge to the Zagreb aquifer, what can potentially be result of a climate change.