The Baidu index (BI) of allergic rhinitis (AR) and the meteorological elements from near surface observation during 2021 to 2023 were used to evaluate the impact of the meteorological factors change on the incidence rate of AR in China. The analyses of the meteorological factor change and the synoptic process reveal a good correspondence between the rapid increase of AR-BI and the early cold air activities during the shift season from Autumn to Winter. The rapid and significant decrease in the daily minimum relative humidity (RH), the daily minimum specific humidity and the daily minimum equivalent potential temperature during the cold air intrusion is synchronized with the rapid increase of the AR-BI from its background value. During the first or early cold air activities each year, the air humidity decreases rapidly and significantly from the range that is more suitable for the human body in Summer and Autumn (RH>40%), which may damage the nasal mucosa and could be the main cause of the high incidence of AR during the shift season from Autumn to Winter, resulting in the period with a high AR-BI from early August to mid-September each year. The influence area of the cold air gradually expands from the north to the south over China during the shift season from Autumn to Winter, while the dry and cold air with lower humidity also gradually advances from the north to the south, resulting in the beginning and ending time of the AR-BI peak (i.e. the high incidence period of allergic rhinitis) gradually delays from the high latitude areas to the low latitude areas. The variability of the AR-BI index is significantly higher in the north than in the south. Compared with the south, the cold air has a more significant impact on the northern region, resulting in lower specific humidity and a greater decrease of air humidity in the northern cities, which may lead to a higher incidence rate of AR in the north.