Statistical analysis of 4-year observations of aerosol sizes in a semi-rural continental environment

► We provide long-term observations of new particle formation in a semi-rural continental environment of the U.S. ► Seasonal frequency of new particle formation is higher in the spring and fall than in summer and winter. ► Nucleation and growth rates show different seasonal variations. ► The frequent occurrence of new particle formation is related to the transported air masses from polluted power plants.