So, I am going to start blog entries on winter. Before that, let's learn about autumn (or I use 'fall' throughout this blog title).
From the Met Office:
When is Autumn?
Autumn is the transition season between summer and winter, best noticed by the colour change in leaves and the harvest.
Perhaps the most noticeable sign of autumn in the UK is the changing colours of the leaves. As a result of the falling temperatures in autumn, the chemical in the leaves that makes them green (chlorophyll) begins to break down while other chemicals (including Carotene) remain to give the leaves their yellow, red and brown colours.
The most vibrant displays of autumn leaves are evident when a dry summer is followed by an autumn with dry, sunny days and cold, but not freezing, nights.
Autumn according to the meteorological calendar begins in September and ends in November. In the astronomical calendar, the beginning of autumn is marked by the autumn equinox which occurs around the 22 September.
During the autumn equinox the sun shines directly on the equator and day and night around the globe are of almost equal length - a day and night of roughly 12 hours each.
Autumn has been significant in many cultures throughout history and even today many festivals and events around the globe occur around the autumn equinox, for example the Moon Festival in China or Michaelmas in the UK (more here).