Cyclone Yasi strengthened to a Category 3 on Monday with winds up to 115 mph. Evacuations are already in place.
The system is expected to hit Queensland on Wednesday or Thursday as a Category 4 storm.
Australia has already suffered months of flooding since heavy rains began in November.
The floods have killed at least 35 people and damaged 30,000 homes and businesses.
The Associated Press contributed to this report.