National parks in Serbia are sensitive to various types of natural hazards that are becoming more frequent and having a significant negative impact on the environment. The present study examines the effects of weather conditions on wildfires in the national parks (NPs) Tara, Djerdap, and Kopaonik using data from meteorological stations and applying climate indices based on air temperatures and precipitation. It examines the variability of fire occurrence dynamics, which depend on changes in the forest aridity index (FAI), the De Martonnearidity index (IDM), and the Lang’s rain factor (AILang) during the period 2005-2021. The highest number of fire occurrences was recorded in NP Tara and NP Djerdap, and the lowest in NP Kopaonik. The risk of fire was greatest during September (27.5%) and August (18.1%), when air temperatures were high and precipitation was low. The fire season was longest in NP Djerdap (February-December) and NP Tara (March-November), and shortest in NP Kopaonik (April-August). Due to the weak correlation between the annual number of fires and individual values of climate variables and climate indices, multiple linear regression (MLR) models were developed. The highest correlation and coefficient of determination were obtained using temperature, precipitation, IDM, and AILang as predictors for NP Tara and NP Djerdap but not NP Kopaonik, where only three wildfires were recorded.