Dumpsites in Lagos raise the contamination of the environment. This study aimed to determine radon exhalation rates and their changes with meteorological parameters on six dumpsites using the accumulation method. The result uncovers the critical relationship between radon concentration and relative humidity at a 5% (p < 0.05) level. Radon exhalation rates varied between 20 and 50 mBq− 2 h− 1. This study is an illustrative map and an essential reference for studying the pollution from radon gas and its impact on the region’s residents, especially as it poses a threat to their health.