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Higher air temperature and increased ambient ozone (O₃) concentration have been associated with childhood rhinitis risk. However, the potential mediating role of elevated O₃ in the increased childhood rhinitis risk due to higher air temperature exposure has not been examined. This large-scale cross-sectional study included 40,103 preschool children from 7 Chinese capital cities. Information on ever-rhinitis, current-rhinitis, and doctor-diagnosed allergic rhinitis (AR) was collected using a standardized questionnaire. Average air temperature (TEMavg) and O₃ concentration in the whole year, warm season, and cold season were estimated at 1 km spatial resolution. The findings revealed that exposure to higher air temperature (annual TEMavg, warm season TEMavg, and cold season TEMavg) and ambient O₃ (annual O₃, and warm season O₃) were associated with an elevated risk of ever-rhinitis, current-rhinitis, and doctor-diagnosed AR. Moreover, elevated O₃ concentration played important mediation effects on the relationships between higher air temperature and childhood rhinitis risk, with the mediated proportions ranging from 19.92% to 35.14% for the whole year, 18.62% to 32.82% for the warm season, and 3.85% to 13.32% for the cold season. Our study highlighted that controlling O₃ pollution may be an effective approach to mitigate the increasing childhood rhinitis risk due to global warming.