The taste of Pu-erh tea is very related to weather conditions. As a rule of thumb, the more rain, the less taste.
Southern Yunnan has a tropical climate: a dry season (September to April) followed by a rainy season. We can separate the tea harvests in four classes.
At the beginning of the year, there is no rain, the temperature is mild, no tea is harvested. In late February, the first buds appear on the trees, here starts the spring harvest. At this point, we produce early spring tea. The leaves grow slowly and the sun shines, the processed leaves can be dried under good conditions.
After the first large rainfall, usually in April or May, we enter in the second period of the tea year: late Spring. This is considered as second quality tea: it is less fragrant and pungent than early spring tea. This is due to the rainfall which increases weeks after weeks.
After rain, the tea leaves grow faster, therefore the output is higher at th expense of quality. Late spring tea is less costly than early spring mao cha. Rainfall and cloudy sky can cause problems to sun-dry the leaves, that can lead to poorly processed teas with disturbing sourness and off flavors.
In July and August, the monsoon reaches its peak. The trees produces high amounts of leaves but the quality is low. Most of the tea cannot dry properly due to the quasi permanent rain. Summer tea is mostly fermented and transformed into Shu Pu-erh. It can also be found in the lower-end raw cakes.
In September, the rain gets more scarce, the clouds slowly vanish and the tea trees give less and less leaves. In late autumn, very decent tea can be found in areas where rain has stopped. Autumn tea is more quiet than early spring tea, it is more Yin, more gentle, and powerful as well.