Final answer:
The main cause of weather is changes in air pressure, influenced by sunlight heating Earth's surface and variations caused by Earth's rotation and seasonal changes.
Step-by-step explanation:
The main cause of weather is changes in air pressure. Weather on any planet with an atmosphere, including Earth, is the result of the circulation of that atmosphere. The primary energy source driving this circulation is the sunlight that heats the planet's surface. Weather patterns are influenced by both the planet's rotation and the seasonal variations in sunlight. Additionally, changes in the Earth's atmosphere and oceans help redistribute heat from warmer areas to cooler ones. While factors like volcanic eruptions, changes in the sun's intensity, and the greenhouse effect can affect climate and weather patterns, the immediate cause of weather phenomena such as wind, rain, and storms is the difference in air pressure across different parts of the Earth's surface.