There are potentially endless natural factors that impact the atmosphere and weather. The activity of the sun, the earth's orbit and tilt, where plants are growing, and what kind of minerals are forming are just a few. The biggest influences on climate are how much energy the earth gets from the sun, how much energy it keeps, and where the energy goes.

In the long term, the type of weather we get most of the time depends on the state of the climate, though in the short term, we can get any kind of weather. The biggest effect that humans have on climate is by changing what gases are in the atmosphere. Vehicles, factories, farms, landfills, and all sorts of other human activities release greenhouse gases, like carbon dioxide and methane, into the atmosphere. With more of these gases in the atmosphere, the earth keeps more of the energy it gets from the sun, instead of reflecting it back into space. This makes our climate (on average, in the long term) get warmer. With an overall warmer climate, the weather gets more extreme (hot, cold, wet, dry, you name it!).

We also affect the atmosphere and climate by removing plants, which decreases the amount of photosynthesis happening on the planet. On a local level, we change the weather by creating urban heat islands. This is another way of saying that dense cities are usually warmer than the area around them. There many reasons for this. One is that pavement is darker than unpaved ground, so it absorbs more heat from the sun. Also, all the cars and electrical equipment release heat. Tall buildings tend to keep the hot air from blowing away, and the pavement stops heat from coming out of the ground and escaping into the air at night.

Weather patterns happen on a very large scale. Weather forecasters can track a system for days before it hits-- just like when they track a hurricane for days before it lands. Since weather systems move over the course of days, only very large natural features affect weather. Big masses of water like oceans, and the Great Lakes can affect weather patterns. Also mountains.

Mountains are a great example of a natural factor that impacts weather. Warm air, like the air over the oceans, can hold lots of water. Air that is at high altitudes, or very cold air, can't hold much water so it is rained out. This is why places on the ocean-side of mountains, like Seattle, are extremely rainy. All the moisture in the air gets rained out in Seattle before the air rises over the mountains. When the air moves up the mountainside, it gets colder and can't hold as much water so it rains. Air on the East side of the mountains is very dry, and so we call the inland side of mountains a "rain shadow". Rain shadows can occur next to any mountain range.

Volcanoes are another natural factor that affects weather. When a volcano erupts, it puts out huge amounts of sulfurous gas. Sulfur gases are what we try to lower in car emissions, because they are not good for the atmosphere. When a big volcano erupts, it can emit thousands of tons of sulfurous gas. When Mount Pinatubo last erupted, the earth's weather temperature was a degree colder for 2 years afterward!

An example of one way that humans affect weather is smog. When human machines make sulfur gases and put them into the atmosphere, it can create smog. In big cities or industrial areas (for example coal mines) where there is lots of pollution (high amounts of sulfur), smog can occur sometimes. Smog is when all the sulfur gas gets trapped close to the ground, instead of being blown away.

This is not a question that is really possible to answer quickly. Weather is an extremely complex natural phenomenon, so anything that influences weather is a natural factor. Humans can alter it, too, by cloud seeding, and in the long-term by altering climate in various ways.

Eating meat and burning fossil fuels are big human factors of global climate change. Erupting volcanoes are big natural factors.

Big fires are both human and natural factors that impact the atmosphere and the weather. The big fires near me are usually due to the electric company's bad maintenance of the electrical transmission lines.