Not normal, appropriate, or expected for the season or time of year.(adjective)
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Use "unseasonal" in a sentence
"Two years ago the trust was warning that "unseasonal" weather could start to spell disaster for many species of insects, birds and mammals."
"As for the "unseasonal" story … Broadcast and The Focus Group also recently commissioned cult soundtrack impresario and Trunk Records founder, Johnny Trunk to write a literary companion to '… Witch Cults …':"
"Food prices in Asia's third-largest economy have hovered at intolerably high levels for close to two years due to rising demand, as well as damage to farm produce due to unseasonal rains late last year."