The Equinox occurs twice a year, the Vernal Equinox in Spring, March 20th for this year and the Autumn Equinox on 22nd September 2012.
On these two days the number of daylight hours equal those of night-time, day and night are pretty much exactly the same length all over the world. This is the reason it's called an "equinox", derived from Latin, meaning "equal night".
Equinoxes occur when the line from the north to south poles, the axis of rotation of the earth, is exactly parallel to the direction of motion of the earth around the sun, and they indicate a change of season.
So for the official first day of Autumn, a ridge of high pressure brings us a cold but bright start, chilly with sunshine for many of us this morning.
Cloud will bubble up later in the day so sunshine turning hazier this afternoon, odd shower around The Wash, temperatures slightly down on Friday’s values at 14-16c, 61f.
Saturday night will be chilly again with a grass frost, especially through the North Midlands.
Weather Alert from the Met Office for Sunday and Monday for heavy rain. Keep updated http://bit.ly/GV70qM
1” of rain expected, possibly 2” locally, over hills.
Sunday and Monday will be the wettest and windiest of the forecastable future with the most persistent rain expected on these days.
On Sunday, the North Midlands will be largely dry but with rain further south.
Monday, showery and windy, gales for Lincolnshire possibly.
Tuesday, another low pressure ‘dumbells’ round the previous one, a day of sun and showers, some heavy.
Pretty much the same forecast up to the middle of next week.