Simplify the following text for a Grade 7 native English-speaking person.
Original: 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 successfully in Iceland .
Simplified: They have a lower summer heat need and are able to survive more rain than other cereals like wheat , rye or barley .