seasonalsea·son·al /ˈsiːzənəl/ adjectiveadj1seasonal adjustment/ change/variation etcCOMMERCE adjustments you make or changes that happen because of the situation during a particular period of the year, that is not typical of the rest of the yearUnemployment figures were down during the summer months, even after seasonal adjustment.
2seasonal business/employment/workers etcCOMMERCEHUMAN RESOURCES happening or needed only at a particular time of yearThousands of agricultural laborers arrive to do seasonal work on American farms.
—seasonally adverbadvFrance’s seasonally adjusted foreign trade deficit