The sun heats the Earth's surfaces, which absorb that heat in varying degree. Air above warm surfaces is warmed, and air cools over cool surfaces. That heating and cooling changes the air's pressure, with the warmer air having a lower pressure and density than the cooler. Air in turn tries to move from regions of higher pressure to those of lower pressure. That movement we call wind.
Wind direction can foretell temperature, humidity, storm or clear.
The moving air can also give a discerning observer the big picture of the great, continually changing air masses making the weather over half of the United States. And sometimes, of course, weather being what it is, all the wind direction tells you is where the wind's coming from. Besides speed, the two major characteristics of wind are temperature and humidity, characteristics it picks up from the region of its source. Thus winds born in the Canadian northland tend to have low temperatures and low humidity, while those that come from the Gulf of Mexico are warmer and wetter. Winds are also seasonal, said meteorologist Jim Travers, with southwesterly winds common in the warm time of year and northwesterly winds the big actor in the cold times.