unseasonable
Definitions
Not characteristic of or appropriate for the current season.
Occurring at an inappropriate or inconvenient time; untimely.
Examples
The unseasonable heat in mid-December caused the flowers to bloom prematurely.
We were forced to cancel our picnic due to the unseasonable rainstorm that swept through the valley.
Synonyms
untimely inopportune ill-timed out of season inappropriate unsuitable