The word "un-seasonable" refers to something that is not suitable or appropriate for a particular season. Its antonyms could include "seasonable," "timely," "appropriate," or "fitting." These words suggest that the thing in question is well-suited to the current season and is in line with what one would expect for that time of year. Other antonyms for "un-seasonable" might include "conventional," "expected," or "traditional." These words imply that the thing in question is in harmony with established norms or practices and is not likely to be seen as unusual or unconventional.