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The spring equinox is here, marking the start of the season when the days grow longer and the trees slowly begin to get their lovely green colour.

But don't be confused if you've heard that spring has already started, you haven't been misled - it actually has two different dates.

There are two separate weather seasons - one is the meteorological season and the other is called the astronomical season.

Let's take a look at what they both mean.

What is the meteorological season?

Weather forecasters split the year into four seasons of three full months.

It helps them to easily compare seasons from one year to the next.

That means every year spring begins on 1 March and lasts until 31 May.

According to the meteorological season, spring has officially already begun.

What is the astronomical season?

Then there's the astronomical season determined by the Earth's tilt as it travels around the Sun.

The astronomical season depends on the date of the spring equinox - that date comes later and varies a bit from year to year.

This year, the spring equinox falls on Wednesday 20 March, and the astronomical spring lasts until the summer solstice.

The summer solstice will fall on Thursday 20 June.

Equinoxes and solstices

But hang on, what's an equinox, what's a solstice, and what's the difference between the two?

An equinox is when the Sun passes directly over the equator - the imaginary line half way between the North and South poles that runs round the Earth. There are two equinoxes each year, one in spring and one in autumn.

During an equinox, day and night are roughly equally as long as each other - in fact, the word equinox comes from two Latin words meaning "equal" and "night".

The equinoxes happen twice a year - on or around mid-March and mid-September.

Solstices on the other hand mark the longest and shortest days of the year and take place when the Sun reaches its most northerly and southerly points.