From the picture below, we can sum up what weather is special and what is the direct influence of temperature, precipitation and humidity.

I study the atmosphere, but this question is really difficult to answer. I have little knowledge. Tell me what I know, not all!

Let's look at the relationship between precipitation and humidity. Precipitation and humidity should be positively correlated, that is, the greater the humidity, the more precipitation. Of course, there are other factors, such as upward movement and atmospheric stratification. Judging from the graph you gave (only the two curves of precipitation and humidity), only the corresponding relationship between precipitation and humidity in April is not good (not positively correlated), and the other times are basically the same.

The change of humidity depends on the water vapor transport at high altitude, which is not directly related to the temperature, but changes with the seasons (the picture you gave is from China). China is a typical monsoon region, with northwest wind prevailing in winter and dry and cold air. Southeast winds prevail in summer, and the air is warm and humid. Of course, precipitation is concentrated in summer.

* Details, you can ask, I will consider.