Fires in NSW and Queensland have led to the Red Cross closing its donor centres at Taree, Coffs Harbour and Port Macquarie, and the pop-up centre at Byron Bay.

The Red Cross fears that, with these centres closed and donors cancelling appointments in other nearby locations, blood supplies could start to run low.

Spokesperson Helen Walsh said they need people around the country to roll up their sleeves.

"Given the unpredictability of the fires, the reality is we're unlikely to immediately know the full impact on donations until later in the week. We do know that we collect around 15 per cent of blood supplies for NSW in the areas where we have had to close our centres," she said.

"In addition to the blood centre closures and with catastrophic fire warnings in place for much of the east coast, we are expecting to see an increase in donors needing to cancel their appointments at our Maitland, Newcastle and Gosford centres at a minimum.

"With blood being a critical resource, we simply cannot afford to take a wait and watch approach and are calling for donors to please roll up their sleeves, now, in order to bolster the nation's blood stocks."

The Orange Blood Donor Centre - 84 Kite Street is open for the following hours:

People are encouraged to make appointments by calling 13 14 95.