Wildfires enhance surface PM2.5 concentration and thus adversely affect air quality and human health. Based on online-coupled fire-climate-ecosystem model simulations, this paper projects a nearly 2-fold increase in wildfire-induced summer-mean surface PM2.5 by the mid-21st century over North America. The projected enhancement is substantial even in the less-densely forested eastern US - as already manifested in the poor air quality as observed in June 2023 due to Canadian wildfires -, which is attributed to the transport of smoke from North America as well as positive climatic feedback of smoke on PM2.5. Thus, future regulatory controls on PM2.5 in North America, particularly in the eastern US where anthropogenic emissions are falling, should consider the effect of future increases in wildfires.