HAIL and flood damage throughout the WA grainbelt last week has caused an immediate but slight downgrade of 250,000 tonnes in the State's estimated grain harvest of 13.45 million tonnes.
However the real toll on crop quality and volume won't be fully understood until grain deliveries start arriving in larger volumes at CBH grain bins when harvest ramps up.
CBH general manager of operations David Capper said the hail hit small areas of the Kwinana Zone, around Dowerin and Wyalkatchem, and "hit them really hard".
Mr Capper said areas in the western part of the Albany Zone and through to Boyup Brook and some areas east of Esperance also received hail.
"Overall hail doesn't have a massive impact on the State's final total but it's obviously devastating for the growers it does hit," he said.
Mr Capper said last week's wild weather was also marked by heavy rain and flooding which caused the most damage in the Albany zone, through the Lakes area.
"The majority of losses have come from the water damage from the heavy rain rather than the very devastating damage in small areas from hail," he said.
"Last year's harvest was perfect in terms of weather but the two before that were very wet.
"In 2011-12 we had 400mm of rain during harvest. We're a long way off that this year.
"We've certainly had worse starts than this one but we'd certainly like to have a clear run from here."
Last week's heavy weather caused CBH to revise its forecast downwards by 250,000t in the Albany Zone.
Mr Capper said the estimated returns in the Geraldton Zone remained steady at 2 to 2.1mt, along with Kwinana (6.5mt) and Esperance (1.6mt) but Albany's forecast is now 3.25mt.
He said the Albany Zone had only received 500t of grain this harvest, as of Monday, making it too soon to judge the final impact on crop quality.
"We have revised our estimate down in Albany by about 250,000t as a result of water and hail damage," he said.
"But in terms of the remaining crop and what impact it will have on the actual quality, it's far too early to tell but hopefully we'll start seeing some more grain coming in this week."
Mr Capper said the grain delivered late last week in the Kwinana Zone, and over the weekend, seemed unaffected by the flood and hail storms.
"It doesn't seem to have had too great an impact on the grain that's been delivered but the volumes are too low to get a good gauge on," he said.
"Hopefully we'll see over the next week or so, how good the quality is."
CBH Kwinana Zone manager Gavin Bignell said some farmers had definitely lost yield of 70 to 100 per cent of certain crop varieties, in a relatively small isolated area running in a strip from Konnongorring to Wyalkatchem and Dowerin.
He said the final crop volume hadn't been downgraded due to the wild weather and there were no recorded issues regarding grain quality.
Mr Bignell said most of the rain occurred south of the Great Eastern Highway where most of the crop remains green.
He said by the end of last week more than 300,000t of grain had been delivered in the Kwinana zone with the majority being canola with a little wheat and barley.
Kojonup Farmanco agronomist Chris Robinson said about 1000 hectares of cropping land was hit by another hail event last week which saw some wheat, barley and canola growers suffering about 50 per cent to 100pc wipe-out or crop loss.
He said the storm produced 20 to 30mm of rain in under an hour but hail stones ranging 30mm to 80mm caused all of the damage.
However, Mr Robinson said the Kojonup area was still looking at above average yields for the year with most growers "having a fantastic spring", while canola growers are a week or so out from swathing.
Parts of the Esperance Zone received rainfall of about 130mm however CBH Zone manager Mick Daw said the impact on grain quality and volume also remained unclear.
He said canola was starting to "trickle in" to CBH grain receival points carrying some mud and dirt, "but that's only while paddocks are still wet".
"We only had a small amount of hail damage - some out Condingup and Beaumont way - and there will be some yield loss, but not significant," he said.
"Most of the loss will be around some of the canola crop that has been swathed and was blown around or rained on."
Mr Daw said about 50,000t of grain had been delivered across the Esperance Zone, since harvest started on October 9.
The storm also impacted on crops in the Kwinana Zone around Dowerin and Wyalkatchem, with some flattened due to hail.