The Insurance Council of Australia (ICA) has declared Cyclone Debbie a catastrophe and warned that, while there is no estimate of a damage bill yet, previous cyclones have cost billions of dollars.

Key points: Insurers brace for billions of dollars in claims and declare a catastrophe

Insurers brace for billions of dollars in claims and declare a catastrophe Qantas cancels flights to Townsville, Mackay, Hamilton Island, Proserpine and Moranbah

Qantas cancels flights to Townsville, Mackay, Hamilton Island, Proserpine and Moranbah Economist Craig James says economic impact likely to be limited due to cyclone's timing

More than 90 per cent of North Queenslanders have some kind of insurance coverage and most home and contents insurance policies cover cyclone damage, according to the ICA.

The ICA will declare an event to be a catastrophe when it results in a large number of claims and involves multiple insurers.

The council's general manager of communications, Campbell Fuller, told ABC News 24 that insurers are gearing up for a deluge of claims.

"Once the cyclone has passed and it's safe to do so, ring your insurer, find out what's available to you under your policy and the insurer can then give you the best guidance on the next steps to take," he said.

"A building [that] looks perfectly fine from the outside or seems to have suffered only minor damage may have actually incurred hundreds of thousands of dollars of damage and that's even for newer buildings."

Events declared as a catastrophe: Insurers cannot discourage claims being lodged

Insurers cannot discourage claims being lodged An initial decision on claims has to be made within 10 days

An initial decision on claims has to be made within 10 days A final investigation and decision will take no longer than four months

Major insurer Suncorp said its claim costs from the cyclone are expected to be fully covered, with its reinsurance providing cover for the company for claims totalling from $250 million up to $6.9 billion.

Cyclone shutdown

Companies have shut up shop and flights have been cancelled as Cyclone Debbie begins to make landfall on the mainland between Airlie Beach and Bowen.

A number of businesses have suspended operations in the region, with Glencore announcing yesterday that port operations in Townsville, Abbot Point and Dalrymple Bay have been halted while production at its Collinsville and Newlands coal mines have been temporarily suspended.

Qantas and Jetstar have cancelled all flights to Townsville, Mackay, Hamilton Island, Proserpine and Moranbah today.

Flights may resume on Wednesday depending on the weather in North Queensland, Qantas said, adding there is a fee waiver in place for affected customers.

Some businesses are also providing assistance to customers affected by the cyclone.

ANZ said it would suspend repayments on loans and waive some fees, while the Commonwealth Bank also announced that it would have special arrangements in place to support customers.

Economic impact should be muted

Analysts expect the cyclone will have minimal impact on broader Australian economic growth, as the weather event is hitting late in the March quarter.

"Any delays to production should be caught up over the June quarter," Craig James, chief economist at CommSec, wrote in a note.

"Any repairs to damaged buildings and infrastructure will boost economic activity over coming quarters."

However, there are fears surrounding the impact of the cyclone on sugar crops in the Bowen-Mackay region.

About a quarter of all sugar produced in Australia comes from the Mackay-Proserpine region, according to the Australian Sugar Milling Council.

"Including Herbert-Burdekin, 62 per cent of all sugar produced in Australia comes from cyclone-affected regions with production estimated by Canegrowers at $1.1 billion," Mr James wrote.

The sugar harvest generally begins around early June.

The Bowen region is also a key producer of fruits and vegetables - including mangoes, tomatoes and capsicum - with any destruction or delays to vegetable supplies causing prices to rise.