It is obvious that solargraphy gives immediate information about the cloudiness. However, using the other property of the black-and-white photographic paper, the rainy periods may be estimated also. The paper increases its sensitivity when it is humid. Also after a rain its reaction on the light is different. This can be seen in the above image. Color gradient in the middle of the image changes from white to purple after the last rain. In the top of the image the gradient is green-yellow-purple. In april there was a light rain, which can be seen from not high change of the solar trail color. The color bar imposed in the center of the image is incomplete and gives a rough view on the weather conditions only. One can't say exactly when the rain occurred during rainy season. One knows that during this period (marked with blue) the rain occured surely. But looking at the last 4 days it is clear that there were particular days with: rain, Sun, clouds, and Sun. Any comments are welcome. Please find the contact information in my Bio section. Thanks to Adam for rapid comments.
This photo is dedicated to my daughter Lucie born 21 August 2015.