Simplify the following text for a Grade 10 native English-speaking person.
Original: The series was ratified by the FÃ dÃ ration Internationale de l'Automobile ( FIA ) and races were held in the traditional Formula One off-season , the northern hemisphere winter .
Simplified: The series was ratified by the FÃ dÃ ration Internationale de l'Automobile ( FIA ) . Races were held in the traditional Formula One off-season , winter the northern hemisphere .