Temperatures in the Central San Joaquin Valley averaged 380C from 16-19 May causing citrus trees to lose abnormally high levels of young fruit. Strong winds immediately followed causing even more damage. Unofficial industry estimates peg next season's navel crop at around 60m cartons – 30 per cent down on 2008. The USDA will release its forecast in September.

'Next year’s crop may have the shortest yields in 20 years,' Barney Evans of Sun Pacific Shippers said. 'The volume would be off even more except for increases in acreage. But it’s not only navels that have been hit but valencias and clementines as well.'

California stonefruit crops have fared better, as industry organisations report little if any damage from the extreme May weather.