"We are giving Mother Nature a bit more time though," Mr Mooney said, adding the final decision would likely be made this Friday, although with no rain on the horizon he was not hopeful.
"It would be disappointing and sad to lose the old chuffer but, at the end of the day, when you take the fire risk into account, it is not a hard decision to make."
However, he said as the big dry continued a "Plan B" was being put in place in the form of an equally historic old diesel locomotive, also restored and operated by Steam Incorporated.
The diesel, built in Australia in 1957 and which operated on New Zealand tracks until 1988, is only one year younger than the steam locomotive which has done the Art Deco trips for the past decade.
"So it's still an oldie and it doesn't need a fire permit ... it just doesn't have the chuff sound."
However, those booked for the string of short and long-journey excursions between February 14 and 17 would still enjoy the experience of travelling in carriages which date back to Art Deco times and styles.
The trust has been contacting people booked for steam excursions, advising that coal-fired was likely to be replaced by diesel powered this year.
He was not aware of any cancellations at this stage.
There would, however, have to be alterations made to the timetables, because the diesel did not require the time-consuming fuelling and turnarounds, and also travelled more efficiently on return journeys.
There would be return time adjustment between 30 minutes and two hours on the longer runs.
Exactly 10 years ago, during the Art Deco Weekend of 2003, the steam train was also in jeopardy as the result of dry conditions, but a permit was granted "at the last minute" as conditions eased.
