Mountains within alpine regions can have a significant influence on the geographic distribution of precipitation and on local- to regional-scale climatic and meteorological conditions. Consequently, the oxygen and hydrogen isotope compositions of precipitation are affected by alpine topography as well. The Austrian Network of Isotopes in Precipitation, one of the oldest and densest networks in the world, is therefore an excellent source of isotope data of the last 30 years for investigating the complex processes governing the isotopic composition of precipitation in alpine regions. Fractionation during phase change processes leads to significant isotopic variation in precipitation. Here we show that the spatial isotopic variability, especially in alpine regions, is to a large extent due to nonequilibrium fractionation. Additionally, we conclude that meteorological conditions prevailing at the sampling site are mainly responsible for the observed seasonal pattern in deuterium excess. These results are validated by stepwise multiple regression as well as by applying an empirical model for deuterium excess, which is an indicator of the differential behavior of D and 18O values in vapor and precipitation. The present results enhance the development of models based on detailed statistical assessment of local climatic conditions to improve the quantitative interpretation of isotope data for paleoclimatology delivered by glacial ice of alpine regions.