Seasons in Earth Due to Inclination of Rotation of Axis

How about Wikipedia?

It varies between 23.1°. and 23.5°.

At present it may be 23.4°.

Are you asking what caused the Earths' tilt, which is currently about 23.4 degrees? The most likely cause was an impact with the proto-Earth that occurred about 4.5 billion years ago which created the Moon.

http://en.wikipedia.org/wiki/Giant_impact_hypothesis

This is the leading theory for the formation of the Moon. Much of the evidence for it comes from discoveries made during the Apollo Moon landing program.

The main effect is the spreading out of sun rays with changing angle of incidence.
If the sun is directly overhead, a square meter of "rays" hits one square meter of ground. If the sun is 45 degrees down from overhead, a square meter of "rays" hits 1.414 sq m of ground.

Check this out!

http://wiki.naturalfrequency.com/wiki/Seasonal_variation

Elliptical shape in geometry is like making an egg on paper.you place Sun in centre of ellipse(shape made) and draw sketch of earth on outer path (on ellipse) in inclined position on its axis.Now divide the elliptical path horizontally and vertically from centre then these 4 quarters of elliptical shape reflect 4 positions of earth in a year.You can see in vertical positions both halves(top/Bottom or north /south) of earth are equidistant from sun but in horizontal position top is closer in one while bottom is closer in other.This is the reason for variation of seasons.

Hello dh,

I think many of the responses are good so far, but I wanted to add a little.

While the axis of rotation is significant to the amount of sunlight striking any given locale's surface, how that affects weather patterns becomes a more global issue and not just a matter of that region's amount of solar energy received. For instance, you live at about 13 degrees north, so nearer the equator, your seasonal changes might not be as dramatic as are mine at 41 degrees north ... my daylight ranges from about 15 hours to about 9 hours seasonally, whereas your daylight ranges from about 13 hours to about 11 hours. This difference affects my climate more than it does yours, however, the global changes as a result of this seasonal change is more dramatic.

Weather, as it changes seasonally, is a dynamic effect of the geology and geological events, earth's rotation, lunar, planetary, and solar affects, and global temperature of the entire planet. While general conditions can be predicted seasonally and annually, the specific conditions cannot. [this year, the midsection of the United States suffered an unprecedented drought.] While our 'model' of weather prediction has improved vastly, it is far from exact.

I found this site in my own searching which may help some ...

http://www.fas.org/irp/imint/docs/rst/Sect14/Sect14_1c.html

I learned a lot from this, and while it cannot help me predict specifics, it does help me to understand some of the 'why'. Sorry that this site tends to look only at North America, but there may be other sites with a more global perspective. I searched "global weather patterns" to find this.

Kind regards ...

The MILANKOVITCH CYCLES, I think is what you are looking for?

http://en.wikipedia.org/wiki/Milankovitch_cycles

Regards JD.