Oats are grown in temperate regions. They have a lower summer heat requirement and greater tolerance of rain than other cereals, such as wheat, rye or barley, so are particularly important in areas with cool, wet summers, such as Northwest Europe; they are even being grown in Iceland to help prolong the growing season. Oats are an annual plant, and can be planted either in autumn (for late summer harvest) or in the spring (for early autumn harvest).