Agricultural irrigation practice is one of the important anthropogenic processes in the land surface modeling. Irrigation can decrease local surface temperature about a few ℃ with alternating surface energy partitioning. Rice paddy is the major food crop in Asian monsoon region. Rice is grown under flooded conditions during the growing season; hence, the rice paddy can be considered as an open water body, which has more impacts on the surface energy budget than other cropland does. In this study, we will explore how the rice paddy area changes affect Taiwan’s regional climate from both observational data and numerical modeling exercise. In this study, the Weather Research and Forecasting (WRF) model is utilized to explore the impacts of rice paddy area changes on the regional climate and energy and water budget changes. In addition, temperature datasets from 6 automatic weather stations in the northern Taiwan and 2 stations in the southern Taiwan are analyzed in this study to explore how the Daily Temperature Range (DTR) changes with the decreased rice paddy areas. WRF is also utilized to test the potential impacts on the wind pattern and precipitation changes. Simulations from 18 weak synoptic environment cases show that temperature increases about 1℃ to 2 ℃ in the daytime, but decreases about 1 ℃ in the night time. Onshore wind component also increases 1~3 kts in the afternoon due to an increased in the land-sea heat contrast. Simulations from another 16 cases in the unstable environment show that precipitation is more in the fallow region, but fewer in the surrounding areas around the fallow region. Previous studies showed that due to the urban heat island effect, aerosol direct and indirect effects, and global warming, the DTR has decreased in the past 4 decades observed from most of the weather stations around Taiwan. However, the declined rice paddy area may increase the DTR with higher Bowen ratio during the daytime. In this study, DTR is decreased in weather stations near the urban area, but increased in weather stations near fallow areas in the past 20 years. It shows that different land use changes may have opposite impacts on local and regional climate.