Cave microclimate is prone to important changes in certain passages due to intensive tourism. Monitoring the climatic parameters (air temperature, CO2) in Postojna-Planina Cave System helps to have a proper picture of the impact of tourism for the cave. It is very useful to compare if additional increase of temperature is associated with the changes at the surface climate. The dataset comprises two types of daily mean air temperature data: 1) the daily mean air temperature data (°C) measured in “Lepe jame” cave passage from Postojna Cave, counting constantly a very high number of tourists; the measurements were made in the same point, by three sensors placed at three different height points (in the wall cracks [T1], at ceiling level [T3], and at 2 m height [T2]). Values are recorded at 10 min intervals and then averaged for daily data (the dataset for Lepe jame cave passage is provided by MEIS Environmental consulting d.o.o. (http://www.meis.si/) while the data are part of the project "Assesment of natural and antropogenic processes in micro-meteorology of Postojna cave system by numerical models and modern methods of data aquisition and transfer" [https://izrk.zrc-sazu.si/en/programi-in-projekti/assesment-of-natural-and-antropogenic-processes-in-micrometeorology-of-postojna#v]; 2) the surface daily mean air temperature measured at 2 m height (°C) at the Postojna meteorological station, as part of the national network of meteorological stations within the Environmental Agency of the Republic of Slovenia (ARSO; http://meteo.arso.gov.si/).