Exploring heatwave in urban and rural areas across urbanization stages

The current global trend of heatwave events is becoming increasingly frequent and severe, closely linked to climate change and global urbanization processes. Studies have shown that urbanization exacerbates the urban heat island effect, thereby increasing the risk of heatwave events. Existing research often employs a binary urban-rural perspective to explore the impact of urbanization on heatwaves. However, the impacts of heatwaves on cities at varying stages of urban development—ranging from rapid growth to counter-urbanization—remain inadequately understood. This research addresses this gap by analyzing observational data from the Global Historical Climatology Network daily (GHCNd) over 1990–2020, classifying cities based on their urbanization processes (e.g., S-curve dynamics or counter-urbanization). We examine how these developmental stages correlate with heatwave frequency, duration, and exposure amplification—a novel metric reflecting the pressure of coping with heatwaves, calculated as the ratio of heatwave exposure growth to heatwave event increases. Results reveal that 22.2% of urban stations show statistically significant trends in heatwave metrics, with three-quarters experiencing increased heatwave days. Cities in medium or advanced urbanization stages exhibit pronounced heatwave escalation, while rural areas display divergent responses. Notably, cities in early urbanization phases face the strongest heatwave exposure amplification effects (exceeding 200%), indicating faster growth in exposure than in heatwave events. This effect diminishes with urbanization progress but, spatially, lower-latitude cities endure more severe amplification effects, compounding challenges in already high-temperature regions. In addition, rural areas adjacent to urban zones also show elevated vulnerability, with future projections under Shared Socioeconomic Pathways (SSPs) suggesting rural populations may face greater heat exposure risks than urban counterparts. The study provides targeted insights for policymakers to design adaptive strategies, emphasizing the necessity of considering urbanization stages in climate resilience planning.