BACKGROUND: Acute kidney injury (AKI) is associated with progression to chronic kidney disease, initiation of dialysis, and a decline in quality of life. Although rising temperatures have been linked to an increased risk of AKI, evidence regarding this association among outpatients in Japan remains limited. This study evaluated the association between community-acquired AKI (CA-AKI) and temperature using prefecture-level aggregated data. METHODS: We used Health Weather, a database integrating Japanese claims data with meteorological information. Among 4,868,549 individuals, we calculated the daily incidence of CA-AKI across 47 prefectures from 2018 to 2019. Associations were evaluated using the Cochran–Armitage trend test. RESULTS: CA-AKI incidence significantly increased as daily mean temperatures rose (p = 0.003). CONCLUSIONS: CA-AKI in Japan is significantly associated with higher temperatures. Preventive strategies should be tailored to the climatic characteristics of each geographic area.