A Year’s Worth of Clues

What number replaces the question mark in this sequence?
7, 8, 5, 5, 3, 4, 4, ?, 9, 7, 8, 8

Hint:The title of the riddle helps with the answer.

6

Each number corresponds to the number of letters in the name of each month:

January → 7
February → 8
March → 5
April → 5
May → 3
June → 4
July → 4
August → 6 ← the missing number
September → 9
October → 7
November → 8
December → 8

18

21