Farmers in the Australian state of Victoria are biting their nails as they deal with their worst heatwave since 1939, following one of the driest Januaries on record.

Temperatures in most of Victoria, as well as South Australia, will be over 40ºC for the rest of the week.

The heat is compounding water availability problems, according to the Weekly Times Now. Irrigation allocations in Victoria are only on about 33 per cent.

Apples and pears were particularly vulnerable to the heat, according to Shepparton grower Andrew Prentice.

'If it gets too hot, the pickers knock off at lunchtime...this sort of weather is not what we need in the middle of harvest,' he said.