The weather bureau has ramped up warnings about the impending dangers of Cyclone Jasper, which could unleash destructive winds of 140km/h and a life-threatening 500-millimetre deluge on north Queensland within hours.

The dangerous system was upgraded from category one to category two on Tuesday afternoon as it neared the far north coast.

The Bureau of Meteorology said extreme gale-force winds would begin in the strike zone around Port Douglas overnight Tuesday and into Wednesday.

The tropical storm was expected to make landfall near the tourist mecca as a category two system about 1pm Wednesday.

“Strong and consistent” winds capable of uprooting trees could strengthen further as the cyclone crossed the coast.

The season’s first cyclone is expected to dump an extreme amount of rainfall, with 250-300 millimetres in six hours, or 500 millimetres over 24 hours. This could lead to life-threatening flooding in the immediate danger zone.

Strong winds are expected to move inland as the cyclone crosses.

Evacuation centres have been set up in Cairns, Port Douglas and Cooktown. A cyclone watch zone extends inland and further north to Cape Melville.

Preparations are well underway in the far north, where a king tide is also looming. Sandbags have been provided in Cairns, with about 15,000 properties at risk of storm surge flooding.

The Cairns hospital is also vulnerable, prompting contingency plans including the cancellation of elective surgery on Wednesday to free up capacity.

A nearby aged-care facility may also be evacuated.

Cairns Airport remains operational but several airlines have indicated schedule changes or flight cancellations.

“Passengers will be advised by their airline of any operational impact related to Tropical Cyclone Jasper,” airport CEO Richard Barker said.

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About 40 police officers and 70 SES workers have travelled to the far north to help.

Cairns mayor Terry James urged locals to stock up and be prepared for up to five days without power.

“The roads will be cut off, potentially the power will be cut off,” he said.

About 450 Energy Queensland staff have been sent to Rockhampton and Townsville in preparation to respond to power outages.

All national parks and campsites north of the Daintree River have been closed. People have been urged to avoid road travel throughout far north Queensland.

“It’s been over 60 years since we’ve had a direct hit,” James said.

“There’s a lot of stories out there that say we’re protected. Well, we’re not protected.”

Police urged the community not to be complacent.

“We certainly hope it will be a low-category cyclone but we plan for the worst so we are working hard to ensure we protect the community,” Acting Chief Superintendent Sonia Smith said in Cairns.

-with AAP