When is spring 2017 in the UK? Why are their two different springs?

Brits will be looking forward to spring even more eagerly than usual after the horrors of storms Doris and Ewan. But when does spring in the UK begin in 2017?

It's actually surprisingly complicated. Depending on which of two definitions of "spring " you choose to employ it's either 1 March 2017 or 20 March 2017. To see why there's a disagreement, read on...

Meteorological spring vs Astronomical spring

Although it is not widely known, there are actually two ways of measuring the seasons. The astronomical seasons are based on the Earth's position in relation to the sun while the meteorological seasons correspond to fixed days on the calendar.

The astronomical seasons tend to be the ones people are most familiar with. They coincide with the equinoxes and solstices - transition points on planet Earth's journey around the sun.

Astronomical seasons do not begin and end on the same day each year. Astronomical spring begins on 20 March 2017 and ends on 20 June 2017.

The meteorological seasons are much more straightforward: they involve breaking the year into four exact three-month periods

Meteorological seasons begin and end on the same day each year. Meteorological spring will begin on 1 March 2017 and ends on 31 May 2017.

What causes the seasons?

The seasons - spring, summer, autumn and winter - are characterised by different kinds of weather and daylight hours. These changes are are caused by the tilt of the Earth as it orbits the Sun.

At different times of the year, different parts of the planet are tilted towards and away from the Sun meaning they receive amounts of sunlight. Plants and animals change their behaviours according to the annual cycle of sunlight hours.

Astronomical spring is marked by the vernal equinox: the point at which the Earth (in the Northern Hemisphere) tilts towards the sun for the first time in six months. It is halfway between the winter and summer solstices. In 2016 it was 20 March, this year it was 21 March.

Meteorological spring will begin, as always, on 1 March. Meteorological seasons were devised to help meteorologists record observations and make forecasts on consistent basis in line with the Gregorian calendar months.