Monitoring of air temperature takes place at five locations in two cave systems. At monitoring location Velika gora (Postojna 1), mean air temperature for the time period 2009–2010 was 11.10 °C. Of three monitoring locations Velika gora is situated at the highest absolute height. Mean air temperature in the same period was 10.66 °C in the central part of the Lepe jame cave (Postojna 3) and 10.30 °C in the side passage (Postojna 2). Temperature difference between outside and cave temperature is the highest at Postojna 2 monitoring location, due to the inflow of the air currents from the unknown parts, especially in winter time. Manual temperature measurements (2004–2010) exhibit slight increase of air temperature at Postojna 1 and Postojna 2 monitoring sites. In the Predjama cave system, the air temperature in Velika dvorana is much more stable than in Konjski hlev passage, which is more subject to external influences.