Final answer:
La Niña could be causing droughts in Australia and floods in parts of South America.
Step-by-step explanation:
If Australia is experiencing droughts and parts of South America are flooded, the weather system that might be occurring is La Niña. La Niña is a climate pattern characterized by cool ocean temperatures in the eastern equatorial Pacific Ocean, which can cause increased rainfall in some parts of the world, including South America, while producing drier conditions in other areas, such as Australia. This phenomenon is the opposite of El Niño, which is associated with warmer ocean temperatures and can result in drought conditions in Australia and increased rainfall in South America.
Learn more about La Niña and its effects on weather patterns in Australia and South America.