Transfer information from one window to the next

[Sonex]

val stream = inputStream.assignAscendingTimestamps(_.eventTime).keyBy(_.inputKey).timeWindow(Time.seconds(3600),Time.seconds(3600))

stream.apply{...}

Given the above example I want to transfer information (variables and values) from the current apply function to the apply function of the next window (of course with the same key).

How can I do that?