Coarse grains are a staple food for large populations in the arid and semiarid regions of the world. This chapter presents the growth, development, and climatic requirements (particularly temperature, precipitation, and photoperiod) of three important coarse grains, namely, maize, sorghum, and pearl millet. The environmental requirements for optimum growth varies with crop species. Most of the progression across growth stages and development is dependent on temperature and photoperiod. All crop species and stages of crop development have cardinal temperatures. Among the three cereals, maize has relatively lower cardinal temperatures, followed by grain sorghum and pearl millet. Total water requirement, water productivity, and response to irrigation is relatively greater in maize than in sorghum and pearl millet. Maize is relatively more sensitive to high temperature and drought stress during sensitive stages of gametogenesis, flowering, and early grain filling stages of crop development. Sorghum and pearl millet can perform better under high temperature stress and drier environments. All three-crop species are short-day plants and respond to changes in photoperiod; however, new hybrids are day neutral. There is large genetic diversity for response to environmental conditions such as temperature, water, and photoperiod, and to biotic stresses. Genetic variability needs to be systematically utilized for breeding to enhance stress tolerance to obtain higher and more stable yields in multiple environments. Projected change in climate and management practices will require a better understanding of crop agroclimatology, so that we can match crop phenology to optimum environments and efficient crop management practices to exploit full genetic potential.