Did ancient people sleep together on rainy days?

The ancient ancestors of China advocated abstinence, saying that overwork would damage the body, so every time they had sex, they were very particular: they could not have sex on auspicious days and after thunderstorms. However, there is a little scientific basis that some unhealthy sperm may be produced in such days and healthy children cannot be born (there were almost no contraceptive measures at that time). Now it seems that they can still do it.