<p>The interactions between meteorological factors, atmospheric particulate matter (PM), and background radiation were investigated in this study. Three databases that recorded these data in Taipei were used and multiple linear regression was applied to analyze the data. It turned out the distributions of meteorological factors, PM2.5 and PM10 concentrations, and background radiation differed significantly between periods of sunny and rainy hours. Background radiation was positively correlated with temperature and relative humidity, but negatively correlated with wind speed on sunny and rainy days. In particular, background radiation significantly increased with PM2.5 and PM10 concentrations on sunny days or nights. However, on rainy days or nights, the background radiation significantly increased with precipitation, regardless of the PM concentration. The effects of PM2.5, PM10 and precipitation on background radiation were found to last up to 1, 5 and 4&#xa0;h, respectively. In conclusion, meteorological factors and PM have significantly different effects on background radiation on sunny and rainy hours.</p>