When does Autumn officially start?

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The calendar has flipped over to September meaning that autumn is not far away. 

Children are returning to school after the six weeks, the nights are starting to become darker and the leaves have begun falling off the trees. 

When does autumn start? (Photo credit should read FRANK RUMPENHORST/AFP/Getty Images)

When does autumn start? (Photo credit should read FRANK RUMPENHORST/AFP/Getty Images)

So it might have started to feel like summer has come to and end. 

However according to the Met Office autumn will not begin for several more weeks. 

Here’s what you need to know about the official start of the season: 

When does autumn start? 

There are two separate dates for the beginning of the season of autumn, according to the Met Office. 

One is defined by the Earth's axis and orbit around the sun and the second is a fixed date which is used by meteorologists for consistent spacing and lengths of the seasons.

The first is known as astronomical autumn and the second is called meteorological autumn. 

READ MORE: Here's what the weather will be like in Portsmouth as September begins

When does astronomical autumn start? 

According to the Met Office when we are usually talking about the first day of autumn it is in reference to the astronomical autumn which is defined by the Earth's axis and orbit around the sun.

In 2019 this begins on September 23 – just over three weeks from today – and it will last until December 22. 

Explaining more about how the start date of astronomical autumn is decided, the Met Office writes on its website: ‘The astronomical calendar determines the seasons due to the 23.5 degree tilt of the Earth's rotational axis in relation to its orbit around the sun.

‘Both equinoxes and solstices are related to the Earth's orbit around the sun.’ 

So when does meteorological autumn start? 

This started on September 1, so has already begun – although the warm weather experienced in Portsmouth over recent days may make it feel like otherwise. 

READ MORE: Commercial vehicle drivers face daily charge if Portsmouth clean air zone goes ahead

The Met Office explains: ‘Meteorological seasons consist of splitting the seasons into four periods made up of three months each.

‘These seasons are split to coincide with our Gregorian calendar making it easier for meteorological observing and forecasting to compare seasonal and monthly statistics.

‘By the meteorological calendar, the first day of autumn is always the 1 September; ending on the 30 November.

‘The seasons are defined as spring (March, April, May), summer (June, July, August), autumn (September, October, November) and winter (December, January, February).’