A tropical low over the Coral Sea is expected to turn into a cyclone over north Queensland this weekend.

A cyclone is expected to lash the north Queensland coast this weekend, with destructive winds and possibly flash flooding, forecasters say.

An alert has been declared between Mackay and Cairns as a tropical low moves in from the Coral Sea, which the weather bureau expects will turn into a cyclone on Sunday.

Gale-force winds are expected to develop around coastal and island communities late on Saturday and into Sunday morning.

Heavy rain, which may lead to flash flooding, was seen as a possibility between Cooktown and Mackay during this time.

A strengthening tropical low was about 570km east-northeast of Cairns and 640km northeast of Townsville on Friday afternoon, as it moved west at 19km/h.

It is expected to intensify, with the weather bureau expecting a tropical cyclone to form on Sunday, which could cross the Herbert and Lower Burdekin coast on Monday.

Areas between Townsville and Mackay could see destructive winds and up to 200mm of rain, Bureau of Meteorology forecaster Dean Narramore told AAP.

“You’re going to get really bad conditions along the coast for up to a day or so,” he said.

If the tropical low forms into a cyclone it will be called Gillian and will be the fourth to hit Queensland this wet season after cyclones Dylan, Edna and Fletcher.