Increasing concurrent drought and heat during the summer maize season in Huang–Huai–Hai Plain, China

Although an individual climate event may not be severe, the concurrence of climate events could have a significant impact on crop production. Investigating concurrent climate extremes during crop growth is important to formulate corresponding strategies for crop production. To assess the occurrence risk of concurrent drought and heat events in the Huang–Huai–Hai Plain (HHHP), China during the summer maize season, we analysed the temporal and spatial patterns of precipitation, standardized precipitation evapotranspiration index (SPEI), drought frequency, and extreme degree days (EDD) during the critical growth period. We used daily data from 41 meteorological stations in the region from 1980 to 2015. We determined that concurrent drought and heat events increased from northeast to southwest. The combined events mainly occurred during the vegetative period, and they significantly increased in 2006–2015 relative to 1981–1990. The spatial distribution of precipitation increased from northwest to southeast, while drought displayed no significant trends. The EDD displayed a rising trend and was intensified after 2000 in different growth periods. Its spatial distribution increased from east to west during the vegetative period and from northeast to southwest during the reproductive period. Although we focused on the combined extreme events for maize in HHHP, similar phenomenon should receive more attention in globally important crop areas and other ecosystems.