Yancoal CEO David Moult said the company's three large opencut mines in the New South Wales continued to assess the flooding impacts and establish recovery plans.
"We currently expect the revised mine plans to enable Yancoal to deliver the 2021 target of around 39 million tonnes of attributable saleable coal," he said.
"Revision to the mine plans, the timing and the type of coal produced are adversely affecting operating unit costs.
"Consequently the full-year cash costs are being pushed to the top end of the guidance range."
The company is forecasting cash operating costs, excluding royalties, of A$60-62 per tonne for FY2021.
"The capable teams at each of the sites are working diligently to mitigate the cost pressure," Moult said.
"Cost guidance is retained at this time while the recovery plans are progressed further.
"Despite the recent disruption to ship loading capacity at Newcastle and flood-affected logistics through the Hunter Valley, Yancoal has the rail and port allocations required to match its production guidance for 2021, so we do not anticipate logistic constraints will affect the guidance."
Moult said the coal price indices continued to recover from the cyclical low in 2020, and the trend was constructive for the 2021 outlook.
"As always, our focus is on the controllable elements of our business, particularly optimising production and reducing operating costs wherever possible," he said.
"This is particularly the case after the production lost during the first quarter due to bad weather.
"Yancoal's low cost of production and ability to blend its output to meet customer requirements mean we are well placed to benefit from the improving market conditions."