Wednesday marked the September Equinox (one of two equinoxes each year - in September and March) when the sun shines directly on the equator and the length of day and night is almost equal.
The September equinox occurs when the Sun crosses an imaginary line north to south above the Earth’s Equator.
On an equinox, night and day are almost exactly the same length, roughly 12 hours each.
For people living at the North Pole the equinox marks the beginning of six months of darkness.
The word “equinox” comes from the Latin equi (meaning equal) and nox (meaning night).
The autumn equinox usually falls on the 22 or 23 September but in 1931, it fell on 24 September.
On the autumnal equinox, pagans celebrate Mabon and the second harvest, beginning preparations for winter, a time to respect the impending dark and giving thanks to the sunlight.
The North American term ‘fall’ was in widespread usage in England until the word Autumn entered English from the French automne, becoming common usage in the 18th century.
Druids meet at Stonehenge greeting the equinox’s arrival as they do for the March equinox and the summer solstice.
But what might the weather hold for beginning of autumn, could there be an Indian Summer in store?
The Met Office forecast and outlook for the end of September:
Blustery and potentially thundery showers on Friday will clear from northern parts leaving plenty of fine, dry weather over the weekend, but the nights will be chilly with mist or fog in places.
High pressure is expected to build across the country from the south over the weekend, bringing a spell of mainly dry and settled weather across central and southern parts.
Further wind and rain may affect northwestern areas later in the weekend.
Dry conditions are likely to prevail through next week and into the following week, particularly for central and southern areas, but occasional bouts of rain and windier conditions may affect northern parts at times.
But an ‘Indian Summer’ is unlikely, with temperatures are likely to be near normal for most part, perhaps warm at times.
Some chilly nights are possible with a risk of local frosts, and an increasing risk of fog patches developing overnight, which could be slow to clear during the mornings.
The Weather Network prediction for October and November: “It is expected to become particularly unsettled thanks to a strengthening jet stream.
“The jetstream usually strengthens going into October, bringing the UK its typical wet and windy autumnal weather.
“However, the pattern of sea surface temperatures out in the North Atlantic at the moment favours a particularly strong jet stream to develop through the autumn.
“As such, frequent spells of wet and windy weather are likely to affect the UK through October and November as deep areas of low pressure are steered close to the country by the jetstream.
“Temperatures will generally be around or slightly below average through autumn as a whole, again thanks to the cooler than sea temperatures out in the Atlantic.”
What is an Indian Summer?
The Met Office defines an Indian summer as a term often used to describe a warm, calm spell of weather that occurs in autumn.
The Met Office blog continues: “Often when we experience a warm period of weather during the autumn months, we hear it referred to as ‘Indian summer’, but what exactly does this mean and where does the phrase come from?
“The Met Office Meteorological Glossary first published in 1916, defines an Indian summer as ‘a warm, calm spell of weather occurring in autumn, especially in October and November.’
“The term was first used in the UK in the early 19th century and went on to gain widespread usage. The concept of a warm autumn spell though was not new to the UK. Previously, variations of “Saint Martin’s summer” were widely used across Europe to describe warm weather surrounding St Martin’s Day (11 November).
“Despite the basis of these phrases around particular dates, there is no statistical evidence to suggest that such warm spells recur at any particular time each year - warm spells during the autumn months are not uncommon.”
The warmest recorded temperatures in the UK in October and November are 29.9 °C on 1 October 2011, in Gravesend, Kent, and 21.7 °C on 4 November 1946, Prestatyn, Denbighshire.