I read that there's

no chance(0%)

a slim chance(30％）

a chance(50%)

a good chance(80%)

we'll get clear skies this weekend.

ここでの good は可能性を示す　⇒high

opportunity ⇔ chance ⇔ probability

probability /,prαːbə'bɪləti/ noun 見込み･起こりそうな事･確率