Simplify the following text for a Grade 9 native English-speaking person.
Original: On July 18 , Estelle intensified into a hurricane , and located in a favorable environment , Estelle continued strengthening to become the first major hurricane of the season on July 20 .
Simplified: On July 18 , it intensified into a hurricane . In an environment that favored an increase of the storm 's winds , Estelle continued strengthening , and became the first major hurricane of the season on July 20 .