Spring is the period from January to March on the lunar calendar, i.e. from the beginning of spring to the beginning of summer; summer is the period from April to June on the lunar calendar, i.e. from the beginning of summer to the beginning of autumn; autumn is the period from July to September on the lunar calendar, i.e. from the beginning of autumn to the beginning of winter; winter is the period from October to December on the lunar calendar, i.e. from the beginning of winter to the beginning of spring the following year. According to the meteorological division, spring is from March to May on the solar calendar, summer is from June to August on the solar calendar, fall is from September to November on the solar calendar, and winter is from December to February on the solar calendar.
Climatically, the four seasons are distinguished by temperature. In the Northern Hemisphere, spring is generally from March to May, summer from June to August, fall from September to November, and winter from December to February each year. In the Southern Hemisphere, the timing of the seasons is just the opposite of the Northern Hemisphere. When it is summer in the Southern Hemisphere, it is winter in the Northern Hemisphere; when it is winter in the Southern Hemisphere, it is summer in the Northern Hemisphere. There are no distinct boundaries between the seasons, and the transition is gradual.