Global warming increases global average precipitation and evaporation, causing extreme climate and hydrological events to occur frequently. Future changes in temperature, precipitation, and runoff from 2021 to 2050 in the upper reaches of the Minjiang River were analyzed using a distributed hydrological model, the SWAT (Soil and Water Assessment Tool), under a future climate scenario. Simultaneously, future variation characteristics of extreme climate hydrological elements in the upper reaches of the Minjiang River were analyzed using extreme climate and runoff indicators. The research shows that the frequency and intensity of the extreme temperature warming index will increase, while those of the extreme temperature cooling index will increase and then weaken in the upper reaches of the Minjiang River under a future climate scenario. The duration of precipitation, the intensity of continuous heavy precipitation, and the frequency of heavy precipitation will increase, whereas the intensity of short-term heavy precipitation and the frequency of heavy precipitation will decrease. However, spatial distribution of flood in the upper reaches is different, and thus flood risk in the upstream source area will still tend to increase. Particular attention should be given to the increase in autumn flood risk in the upper reaches of the Minjiang River.

The intensification of global warming under the influence of human activities has directly led to an increase in the magnitude of changes in the climate system, further exacerbating the impact on the global water cycle and making extreme weather events more frequent and intense. In this study, daily temperature data from 1960 to 2020 from nine meteorological stations in the Qingyi River basin were used to analyze the changes of 16 extreme temperature indicators using extreme temperature indicators, the trend analysis method, and the MK analysis method. The results show that in terms of spatial distribution, the colder extreme events in the basin mainly occur in the upstream and that the warmer extreme events mainly occur in the midstream and downstream. According to the temporal trends of the indicators, the indicators of extreme events with anomalous warming are dominated by a significant upward trend, in which the warm night index increases by up to 3.8 days/decade, whereas the indicators of extreme events with anomalous cold are dominated by a significant downward trend, in which the cold night index decreases by up to −3.4 days/decade. In terms of the magnitude of change in the indicators, the cold and night indicators are more variable. According the spatial difference of index changes, the extreme value index mainly shows a decreasing trend in the upstream of the basin and an increasing trend in the midstream and downstream. Combined with the characteristic of a low extreme value index in the upstream and high extreme value index in the midstream and downstream of the basin as a whole, the spatial difference in the extreme value index in the basin is expected to further increase.