Tra c congestion is one of serious problems in cities; rainfalls would exacerbate tra c congestion, and thus result in huge economic losses. However, limited studies focused on how rainfalls in uenced tra c congestion and its associated economic losses. Based on detailed hourly data, we estimated how tra c congestion index (TCI) changed with different rainfall intensities in the Beijing-Tianjin-Hebei (BTH) region, China, and we also explored their economic losses. The results illustrated that all cities presented the similar trend of daily tra c congestion, and morning peak occurred 2 hours later on holidays than workdays. Rainfall had signi cant impacts on tra c congestion for most time windows, except midnight. Tra c congestion increased with rainfall intensities, but smaller cities were more vulnerable to rainfall intensity than megacities. Rainfalls led to 0.98 billion yuan of extra economic losses in 2019, 38% of which occurred under heavy rainfalls. Tra c congestion in 2019 caused a total economic cost of 31.5 billion yuan in the BTH region (0.4% of its GDP), including the recurrent cost and economic losses due to rainfalls; besides, the social cost and direct cost contributed the same share of 49.4%, with 1.2% from the environmental costs. Considering future urban development and climate change, it is bene cial to establish the climate-resilient transportation system for avoiding future serious tra c congestion as well as huge economic losses in future.