BACKGROUND AND AIM: High temperatures have a known impact on human morbidity and mortality. Few small time series studies have documented associations between acute kidney injury (AKI) and temperature. Studies conducted on agricultural workers found an association between AKI and chronic kidney disease (CKD) of unknown origin. The association between temperature and kidney diseases was less investigated on the general population and on a large scale. The aim of this study is to evaluate the effect of temperature on kidney diseases hospital admissions in Spain. METHODS: Data on daily hospital admission for AKI and CKD were retrospectively collected from 2004 to 2019 in Spain. A Conditional Poisson regression combined with Distributed Lag Non-Linear Models was applied to evaluate the overall cumulative effect of maximum temperature among the 7 days preceding the admission. Models were adjusted for humidity and national holidays, and analyses were also stratified by age and sex. RESULTS: Overall, 244,348 and 39,448 admissions for AKI and CKD were registered, respectively. We observed a J-shaped curve for the association between AKI and temperature with a minimum morbidity temperature of 7°C. The overall cumulative relative risk (RR) at the 99th percentile versus the minimum morbidity temperature percentile was 1.46(95%CI:1.37-1.55). The impact of high temperature remained strong also in the analyses stratified by age and sex with the highest risk observed in the young (<65years) population (RR:1.59; 95%CI:1.43-1.75). Concerning CKD, results were not clear and varied by age and sex. An increased risk of being admitted for CKD in association with high temperature was observed among young males. CONCLUSIONS: High temperatures increased the risk of AKI hospital admissions in the general population, whereas less evidences were found for CKD. Dehydration and hyperthermia caused by high temperatures may stress renal function leading to kidney injury. KEYWORDS:Acute kidney injuries; Chronic kidney diseases; Temperature