A late frost overnight could damage a proliferation of early budding that has developed at least 15 days ahead of schedule.

Murrumbateman winemaker Ken Helm said a mild winter and warm start to spring had triggered early growth in young vines.

''I put that down to their young and impetuous nature, whereas the older more experienced vines have decided this is not quite the thing they should be doing.

''We always tend to worry about at least one frost, usually in October, more often than not associated with a full moon.''

Mr Helm said the full moon was due on October 19, which could mean losses if it coincided with a frost that settled on and subsequently burnt early growth.

''You then rely on secondary buds to come out and they will give you somewhere between 20 or perhaps 40 per cent crop.''

Mr Helm said that this was his 40th year in the district, during which time he had experienced only two very severe frost years. Another scenario is ideal conditions continuing into a hot summer, and a good vintage similar to 2013's, which is now under the noses of judges in Canberra and Murrumbateman.

Murrumbateman Cool Climate Wine Show manager Virginia Rawling said wineries from all over Australia would be judged up until Friday afternoon.

Judging begins on Wednesday for the Canberra and Region Wine Show, where international wine consultant and judge Matt Skinner will preside.

The author of international best sellers, Mr Skinner is co-founder of Fifteen restaurant with Jamie Oliver and Tobie Puttock in Britain.

Mr Helm said the Canberra region show drew wines from the South Coast, Southern Highlands and Murrumbateman, while Murrumbateman's show attracted entries from top regions further afield, including the Margaret River in Western Australia.

The 2013 vintage was exceptional, so competition would be of a high standard.

''They are not running in poor company at these shows. If they win a gold medal, it is a medal worth a lot more than other shows,'' Mr Helm said.