The saying 'make hay while the sun shines' is being met with a wry smile by farmers this autumn after a year of unpredictable and unusual weather.

Frosts in March followed by bouts of excessive rainfall in April, May, June and early in July and then a period of excessive heat have produced unexpected winners and losers for crop growers in Sussex, translating into a matter of profit or loss.

The wet spring proved to be a particular problem for fruit farmers as heavy rains kept honey bees in their hives rather than out foraging and pollinating. Even worse, some hives have been flooded, drowning the bees, and even when bees did venture out, flowers were full of water or heavy rains swept away all their good work. Colder weather during the blossom season meant that little fruit was set.

Fruit farmer Tony Eales, of Tendring Fruit Farm in Hailsham, said he may have lost 90% of the fruit of some of his apple varieties this year. “My crop has been severely affected,” he says. “It'll be 'hunt the apple' for Coxes and Russets this autumn. I doubt if I've got a 10% crop. But other varieties haven't done so badly - Worcester Pearmains are fine because they flower later on.”

Ivor Kiverstein, of Tullens Fruit Farm in Pulborough, also reported crops of Coxes and Russets that were 90-95% down.

Soft fruits such as strawberries have suffered from the lack of sunlight through much of the spring and summer months, with many pick-our-own farms running out of supplies far earlier than normal.

The normal strawberry season normally stretches from early June to mid-August but with pollination down and the low-lying fruit swamped by water, crops were running out during July. Tulleys Farm at Turners Hill near Crawley was warning PYO customers by July 26 that all its strawberries were picked out. “It really has been the most difficult year for pick-your-own strawberries since we started 40 years ago, due to the constant rain and then the extreme heat,” the farm told its customers.

And for the first time in its history, the annual Strawberry Fayre in Walberton in July had to be cancelled. “It was a difficult decision and very disappointing,” says organiser Mike Tristram. “The fields where the event is held were so hugely waterlogged it simply wouldn't have been safe to go ahead. This is the first time in its history the event has ever had to be cancelled.”

But at Fletching Glasshouses, where crops are grown under glass, this year's weird weather has been kept firmly under control. “Because we are growing under glass, we are protected from the weather,” says company spokesman Alan Rae. “We can control how much water the ground is getting, particularly as we have our own reservoir, which is rather full at the moment. We are in a much better position that those growing outside, and because their crops are down, we are finding that we have an advantage.” The company grows between 25 and 30 different crops, including salad leaves, spinach, chard, tomatoes, aubergines and beetroot, supplying local organic shops and markets. Mr Rae says, “A lack of sunlight has put the crops back about two weeks or so but it has certainly not damaged our business.”

The heavy rains, however, have swamped fields of cereals and caused major headaches for arable farmers. Cereals such as barley have been plagued by fungus caused by the wet conditions, which has also made it difficult for farmers to get their machinery onto the fields to gather in their harvest.

Wheat growers are expecting a drop in yield of up to 20%, with a lot of wheat grown for the milling market ending up being sold for animal feed and failing to fetch a premium price. Farmers have been able to cut only one grass crop conserved as silage for winter animal feed, which was cut a month late and past its best. Prices are expected to shoot up due to short supply.

“The quality of the crops is not as good as usual because of fungal disease and low yields due to a lack of sun,” says Ben Taylor, an arable and beef farmer of Iford Farm at Iford, near Lewes. “Combining was about 10 days late, and while it has not affected the beef cows, it will be difficult making winter food for them. We won't have a problem this winter, but I imagine some farmers will and as the price of corn is so high, that will be hard on them. This year has not been a disaster but it is a struggle.”

Sussex's booming wine industry has been watching and waiting to see whether its crops have taken a battering or sailed through. Predictions earlier in the summer suggested that 2012 would not be a vintage year, as the development of grapes was hampered by a delay to the flowering season in the spring caused by dank, dark conditions. And later rains threatened to rot the fruit.

But Sam Linter, head winemaker at the Bolney Wine Estate, says it's far to soon to tell if 2012 will produce a good vintage or not. “We've not been massively hit,” she says. “We managed to stave off frost damage earlier in the year with our frost-busting machines - they're like huge hairdryers, which we used for a couple of days to warm the plants. It kickstarted the flowering so the vines flowered at the right time, before the heavy rains started. I think there will be a lower crop than expected but it will be better than last year.”

Tendring Fruit Farm, Magham Down, Hailsham. Phone 01323 841812.

Tullens Fruit Farm, Tullens Pickhurst Lane, Pulborough. Phone 01798 873800 or visit www.tullens.co.uk Tulleys Farm, Turners Hill, Crawley. Phone 01342 718472 or visit www.tulleysfarm.com Fletching Glasshouses: phone 0845 226 8026 or visit www.fletchingglasshouses.co.uk Iford Farm, Iford, near Lewes. Phone 01273 474614.

Bolney Wine Estate, Bookers Vineyard, Foxhole Lane, Bolney, Haywards Heath. Phone 01444 881575 or visit www.bolneywineestate.co.uk