We assess observed and modeled ozone weekend–weekday differences in the USA from 2002–2019. A subset of urban areas that were NO_x-saturated at the beginning of the period transitioned to NO_x-limited conditions. Multiple rural areas of California were NO_x-limited for the entire period but become less influenced by local day-of-week emission patterns in more recent years. The model produces more NO_x-saturated conditions than the observations but captures trends in weekend–weekday ozone patterns.