The spring drought and cold snap in December 2010 will have a confirmed effect on this year's harvest. Although predictions for oilseed rape yields suggest the UK will harvest its highest ever yield. Winter barley and now winter wheat yields are expected to be reduced in parts of the country that suffered from drought.

In the East, where lighter soils and drier weather meant crops were particularly affected, yields are expected to be down by as much as 50% on some crops because of the drought. Now the threat of rain in these regions means farmers are focusing on bringing in as much of the crop as possible before the rains fall.

Simon Oxley, of the HGCA, however, told BBC Radio 4's Farming Today that yields may still be better than anticipated. He said, "There was doom and gloom a few weeks ago, predominantly down to the drought we had in the spring, but things are looking up, for oilseed rape yields are higher than they have been for the last few years."

Although he acknowledged that prospects for winter barley were not so good at the moment, he remained optimistic. Mr Oxley said, "It does look as though it’s going to be lower, maybe down around 10 per cent, but we have only had about a third of the results in. We may find that by the end of the season it’s on the same level as it was last year."

The latest ADAS figures show this year's wheat harvest is on track. Although some harvesting has begun (less than one per cent of the total plantings) most wheat crops will not be harvested for another week or two; the HGCA said this is typical for wheat harvest which would not normally start in earnest until week 4 of harvest (early August). Many heavy land crops, and those further north, are still very green and harvest of these will be further away.