PARTS of far north Queensland have had more than half a metre of rain in the past 48 hours as ex-tropical cyclone Oswald drenches the region.

The category one cyclone crossed the western coast of Cape York Peninsula near Kowanyama early yesterday, and is now a low pressure system northwest of Cooktown.

It is moving in a southerly direction and forecasters say it could move out into the Coral Sea.

The Bureau of Meteorology has issued a severe weather warning for parts of the far north, saying rain associated with the ex-cyclone and a monsoonal trough could cause flash flooding.

The cane-farming town of Tully, south of Cairns, has recorded more than 600mm in the past two days.

A flood warning has been issued for coastal rivers and adjacent streams between Cooktown and Mackay.

"Forty-eight hour rainfall totals of up to 635mm have been recorded in the warning area to 6.30am on Wedneday, with the heaviest falls recorded between Innisfail and Ingham," the bureau said.

"Further heavy rainfall is forecast for Wednesday and the next few days, with localised totals of 200-300mm possible each day. The rain will extend south to the Mackay area during Wednesday."

Coastal rivers and creeks are rising fast between Cooktown and Ingham, the bureau says.

"As the rain extends further south, fast river and creek rises are also expected in catchments between Ingham and Mackay," it said.

Separate flood warnings are current for the Tully River, Murray River and Herbert River.