Winemakers in Kent are counting the cost of a late frost in April that has damaged vines during the largely hot and dry month.

Some vineyards are preparing to put back harvests for a year after the unexpected clear nights, which allowed temperatures to plummet.

Chapel Down – which has vines in Tenterden, Kits Coty near Blue Bell Hill and the Weald – issued a trading update to shareholders last week insisting its outlook “remains positive despite the frosts”.

However it admitted the potential damage was widespread, although patchy.

Over in Barham, near Canterbury, bosses of the relatively new Simpsons Wine Estate admitted they fear the harvest of some vines planted last year may be put back from 2018 to 2019.

Co-owner Charles Simpson said: “We have had a reality check in the last few weeks from the frost in the UK.

“We bought 10 years of data for this site to see the frost risk. We hoped we had frost free sites but no site is frost free. It’s one of the risks of viticulture.”

Many vineyards protect their young vines with tube-shaped guards, which shield them from pesticides and also act as a mini-greenhouse.

However, when frost strikes it can act like a fridge.

Ruth Simpson, also co-owner of Simpsons Wine Estate, added: “It is too soon to say how much it is going to set us back this year but that’s part of the risk of where we have decided to grow grapes.”

Chapel Down said the April frosts were the most widespread in more than 20 years for the time of year.

Chief executive Frazer Thompson said: “It is a rare occurrence and the outlook for our dynamic English wines industry remains bright.

“The impact of last week’s frosts was mixed with some of our vineyards impacted and some not at all.

“It is far from catastrophic and the truth is that, as ever, we won’t be in a position to gauge the potential crop until after flowering in June.”

The potential damage is a huge contrast to the harvest of 2016, which was one of the best in many years.

Yet frost is not the only potential issue. England had just 30% of its average rainfall in April according to the Met Office but more than average levels of sunshine.

Mr Simpson spoke on a rainy Wednesday morning last week as his firm planted 40,000 chardonnay, pinot noir and pinot meunier vines across 25 acres.

He said: “Doesn’t this just tell you everything you need to know about UK weather?

“At the beginning of April it was 20C and sunny and here we are at the beginning of May and it’s like winter time.

“This year has been very dry. In April we usually have 233ml of rain but in Kent we had just 3ml.

“Thankfully, being on chalk is perfect because, although it is free draining and keeps water away from the roots, it is also a reservoir for water if the vine needs it.”

He added: “We should crop less this year. It depends on the damage from the frost. We welcome the rain.”