Floods is a serious concern across Europe due to the enormous material damage and death toll. Of alltypes of floods, flash floods and large-scale river floods have become major natural hydrological hazardsin most countries. The city of Halmstad was chosen due to its placement on the southern west coast ofSweden, a region for which climate projections have indicated more precipitation and potential forflooding. In recent years a number of floods have also been observed with associated damages. Usingextreme value analysis on observed data these events can be interpreted in terms of return level valuesand their frequency of occurrence. The seasonal variation of the precipitation and discharge of thecatchment were analyzed based on 43-year precipitation and 25-year discharge observation data and therelationship to NAO index was investigated to give a preliminary overview of the hydrologicalconditions in Halmstad and its causes. The results showed that Halmstad was seasonally characterizedby high discharge in winter and lower discharge in summer with the highest rainfall. The effect of stormtracks represented by the NAO index on the precipitation and discharge in winter months was evident.This study focused on the analysis of extreme data of precipitation and discharge. The return levels forup to 50-year return period were estimated by GEV fitting. The estimated return level of discharge fora 50-year return period is 250 m³/s, and the return levels of precipitation for a 50-year flood was foundto be 68 mm/day. Two cases were selected from a compiled annual maxima discharge data set foranalyzing and comparing their weather conditions based on ERA5 data. The results showed that differentweather conditions do have an impact on the total rainfall, and there were similar patterns but largedifferences between ERA5 reanalysis data and observed SMHI data was also shown emphasizing theneed for long-term observational data sets and further evaluation of reanalysis data.