Agricultural drought 1 Air relative humidity Disaster prevention 1 Disasters 1 Drought 1 Drought disasters 1 Food crops 1 Food products 1 Grain (agricultural product) 1 Humidity index 1 Indicator indicator 1 Maize (Zea mays L.) 1 North China Plain 1 Staple food 1 Summer maize 1 The Huang-Huai-Hai Plain 1 The Standardized Relative Humidity Index (SRHI) 1 The huang-huai-hai plain 1 The standardized relative humidity index 1 Zea mays 1 drought 1 index method 1 maize 1 monitoring 1 relative humidity 1 spatial distribution 1 spatiotemporal analysis 1 summer 1