The climate in the Han Dynasty? I have red some an article talking about this. During Eastern Han, the climate had the trend to be colder. There are several severe chilly winter in records. It even snow in late Spring in the capital city, Luoyang, Henan Province. The cold time doesn't last long time anyway. In south Henan Province, orange could grow here but can not have fruits later in the Three Kindoms Period. Generally, the temperature at that time is 1-2 degrees colder than the climate nowadays. In North of Yellow Rover, apricot blossoms came out in MId April and mulberry tree have new green leaves since early May, about 2-4 weeks later than today.