not in keeping with (and usually undesirable for) the season
<adj.all> a sudden unseasonable blizzard unseasonable bright blue weather in November
badly timed
<adj.all> an ill-timed intervention you think my intrusion unseasonable an untimely remark it was the wrong moment for a joke
Unseasonable \Un*sea"son*a*ble\, a. Not seasonable; being, done, or occurring out of the proper season; ill-timed; untimely; too early or too late; as, he called at an unseasonable hour; unseasonable advice; unseasonable frosts; unseasonable food. -- {Un*sea"son*a*ble*ness}, n. -- {Un*sea"son*a*bly}, adv.
Flurries were predicted for the Ohio Valley through New York as temperatures cooled after last week's bout of unseasonable warmth.
Severe cold, high wind and blowing and drifting snow moved into the north-central part of the nation Tuesday, while southerly breezes from the Gulf of Mexico spread unseasonable warmth across the central part of the nation.
The First fan was kept away by an unseasonable blizzard in Washington, but Ron Reagan Jr. did brave snow and paparazzi to attend.
Trees, also, "can also help ensure clean air," Bush said as he planted the tree in a downtown Indianapolis park in unseasonable near-freezing weather.