It's shaping up to be an early harvest for some cherry growers, though the threat of El Niño hangs over the upcoming harvest.

Cherries destined for locals ahead of Christmas are nearing the harvest stage, with picking set to start in just a few weeks.

Mike Casey grows cherries just north of Cromwell and says they looked like green marbles at the moment.

He expected to start harvesting cherries before Christmas this year - about a week or two ahead of schedule.

This was largely thanks to it being one of the warmest springs in over a decade which had also made for a great quality crop, he said.

"It's been great for bringing the trees on early.

"We had reasonable chilling hours. We had really good pollination days. We now have quite an awesome crop on the trees."

Mike Casey says he expects to start harvesting cherries before Christmas - about a week or two ahead of schedule. Photo: supplied

Casey said the final quality of the fruit would be determined by the impacts of El Niño before the harvest.

"Is it going to be wetter for us, which will be damaging for our cherries, or is it going to be nice and dry, in which case we could be expecting one of the best seasons in quite some time?"

He said an early harvest suited his export-focussed business well. Most of the cherries were destined for overseas ahead of Chinese Lunar New Year sales, which is also a few weeks earlier, on February 6 next year.

"It's going to be a really good quality export crop this year if everything goes our way."

Meanwhile, Simon Bishell of Caythorpe Farm in Marlborough grows about 4ha of cherries near Blenheim, alongside a vineyard, sheep and arable operation on the farm.

His cherries are destined for the domestic pre-Christmas market.

He expected to start picking at their usual time at the end of November and said this year's crop was of average size.

"This year, particularly [for] some of our earlier varieties, the weather was a little bit changeable at the earlier start or earlier piece of flowering. So it's sort of been replicated through in the amount of fruit that is set."

Bishell said it was too early to tell what the final harvest quality would be like, as cherries were a "very fragile crop" vulnerable to damage from the rain.

"We hope for a nice fine settled weather period leading into harvest and we can ensure that we have a nice supply of good quality summer fruit available for Kiwis to enjoy this summer."