Seasonable, timely, well-timed, opportune, pat can mean occurring or coming with peculiar appropriateness as to moment or present situation.
What is seasonable is perfectly suited to the season or time of year <seasonable menus for hot August days> <seasonable weather> or, by extension, fits in perfectly with the needs of the moment or the character of the occasion.
What is timely is not only seasonable but comes or occurs at such a moment as to be of genuine value or service.
What is well-timed is so timely as to suggest the appearance or the actual exercise of care, forethought, or design.
What is opportune fits directly into a given concurrence of circumstances or comes as if by accident in the nick of time and works to the advantage of those concerned.
What is pat is perfectly adapted to the situation or the moment or comes or occurs at the very moment it is needed.