The advance of spring phenology and the delay of autumn phenology caused by global warming have been documented by many studies. However, most research has focused on natural areas, with limited studies conducted on phenological observations in urban environments. Here, we selected the first flowering date (FFD), first leaf date (FLD), and leaf coloring date (LCD) at three sites (Beijing, Harbin, and Mudanjiang) from the China Phenological Observation Network. We analyzed the phenological changes of 84 species between 1963–1991 and 1992–2020 to examine their response to urban warming. We then quantified the correlations and regressions between phenological events and preseason temperature. The results show the following: (1) Among the three sites, the mean FFD and FLD were earliest in Beijing, while the mean LCD occurred earliest in Harbin and latest in Beijing. (2) FFD and FLD exhibited a significant trend towards earlier occurrences at all three sites, while LCD showed a significant delay trend except for the Mudanjiang site. Specifically, at the Beijing, Harbin, and Mudanjiang sites, the mean FFD advanced by 8.32 days, 6.11 days, and 2.60 days in the latter period (p < 0.05), whereas the mean FLD advanced by 11.30 days, 7.21 days, and 5.02 days (p < 0.05), respectively. (3) In Beijing, Harbin, and Mudanjiang, both FFD and FLD were significantly negatively correlated with preseason temperature. However, no consistent relationship was observed between LCD and preseason temperature. These results enhance our understanding of the response of plant phenology to urban warming.

Flash drought–induced relative reduction in vegetation activity and canopy functioning, referred to as vegetation sensitivity, is a crucial measure of drought impacts. While climatic factors influencing vegetation sensitivity are well recognized, the role of phenological shifts remains poorly understood. Using multiple satellite-derived vegetation proxies (NDVI, LAI, SIF, and VOD) during 2001–2021, we show that earlier green-up dates (GUD) exacerbate vegetation sensitivity to flash droughts across 61.2–84.1% of the Northern Hemisphere (>23.5°N). Earlier GUDs enhance pre-drought vegetation growth, especially during the early growing season. Such amplified vegetation growth exacerbates sensitivity by accelerating soil moisture depletion and respiration cost, outweighing the benefit of increased subsequent net carbon assimilation. The contribution of GUD to vegetation sensitivity is comparable to that of major climatic factors. Ignoring phenological changes may lead to underestimation of long-term trends in vegetation sensitivity. These findings underscore the necessity of incorporating the interactions between phenology and flash droughts into projections of ecosystem resistance and resilience.