Comic Strips

Simply, when air is heated, it expands. Where does it go when it expands? Whichever direction has the least resistance. That is largely what differing levels of air pressure are. And why we can predict where the air is going to move and how fast. The main thing that determines air pressure is temperature, but there are other complicating factors too. Mountains of course dramatically alter the overall compressibility of air trying to be pushed in their direction. Same with large cities.

Most of the heating of air comes from where on earth is currently lit by the sun, but of course there are also other complicating factors. The suns rays don't directly heat air much, they mostly pass through it of course. But the suns rays heat the more solid objects they eventually touch and those solid objects can spread that heat into the surrounding air. So the heat is dispersed into the air unevenly, depending on what is being heated by the sun in that location. And then of course also the other sources of heat, like the heat coming from the core of the planet, and man-made sources of heat. Both relatively tiny, but factors none-the-less, especially on local-scale weather patterns.

It's pretty complex overall, but also pretty simple if you don't need huge amounts of accuracy.