Hail has already damaged crops in the Mid West and there are concerns heavy rain across much of WA may impact this year's grain harvest.
Co-operative Bulk Handling says parts of the Mid West, Wheatbelt and Esperance regions have received significant rainfall in the past few days.
Farmer Andrew Kenny from Badgingarra says his crop has been badly damaged by hail.
"We've got a couple of thousand hectares of crop and the way the storm went it seemed to follow basically our cropping line all the way down," he said.
"We've got one paddock about 10 kilometres north which is perhaps the only one which hasn't had any damage at all.
"But the others affected, its hard to say, but from 10 per cent to 100 in patches I guess."
CBH Operation's Manager David Capper says with harvest now in full swing, it is crucial the weather clears up.
"There's another front that's crossing the coast on Sunday, that hopefully won't drop too much rain on the area and then it really depends on what happens with the weather after that," he said.
"Whether we get some sunshine and some wind to dry the crops out, if we do then hopefully there will be minimal damage, if the weather stays damp and cloudy and still then unfortunately there could be some damage to the crop from that rain."
© ABC 2012
14:24 EDT Thunderstorms are due to develop daily across New South Wales and Queensland for almost two weeks.