adjective. Not suitable to or appropriate for the season.

adjective. Not characteristic of the time of year.

adjective. Poorly timed; inopportune.

Not seasonable: as, an unseasonable hour. Not suited to the time or occasion; acting at an unsuitable time; unfit; untimely; ill-timed: as, unseasonable advisers or advice.

Not agreeable to the time of the year; out of season: as, an unseasonable frost. Not in season; taken, caught, or killed out of season, and therefore unfit for food: as, unseasonable salmon.

adjective. Not seasonable; being, done, or occurring out of the proper season; ill-timed; untimely; too early or too late

adjective. Not in accordance with the season.

adjective. not in keeping with (and usually undesirable for) the season

adjective. badly timed

"It was one of those days in June, in which our summer-hopes take umbrage at what we call unseasonable weather, though no season was ever known to pass without them."

seasonable  

inopportune  

unseasonableness  unseasonably  

ill-judged  ill-timed  imprudent  inapplicable  inconvenient  

ahead of time  anachronistic  antedated  bad  beforehand