One person's idea of 'comfortable' weather can be unbearable for another. Many travel books have charts and information, but there are also books specifically for weather. Don't try to fine-tune your exact schedule for the optimal weather in each place. Northern Manchuria extends as far north as parts of Southest Alaska. Beijing is at the latitude of Philadelphia, Hong Kong as far south as Havana.
East China gets enough rain year-round for paddy rice.
Much of central China is semi-arid steppe. Similar issues arise in other regions. We hit New Zealand in mid-winter and it was spectacular. And a great contrast to the previous two months on South Pacific islands in the sun. It isn't natural and doesn't give you a true picture.