original: The term is applied both to routine weather variations and to extraordinary spells of heat which may occur only once a century.
simplifications: The term is applied both to routine weather variations and to long spells of heat which may occur only once a century. The term is used for normal weather and for unusual waves of heat that happen very rarely. The term's applied to weather variations and spells of heat which occur once a century. The term is used to describe both routine weather changes and to extraordinary heat spells. Heat spells may occur only once a century. The term refers to both routine weather changes and extraordinary heat spells. These may occur only once a century. The term is applied both to routine weather changes and to extraordinary heat spells that occur about once a century. The term is applied both to normal weather and to unusual instances of heat. The phrase is for normal weather changes and extreme heat spells that may happen every 100 years. The term is applied both to daily weather changes and to period of heat. This rare heat wave may occur only once in 100 years. The term applies both to normal changes in weather and to extreme heat spells which can occur only once a century.