Onion is a cool season crop. However, it can be grown under a wide range of climatic conditions. The ideal temperature requirement of the onion crop is 12.8°–12°C before bulbing and 15.5°–25°C for bulb development. Very low temperature in the early stages favours bolting, whereas a sudden rise in temperature favours early maturity in rabi, resulting in small sized bulbs. Onion can be grown on all types of soils. However, deep friable loam and alluvial soils are best for its successful production.