Seasons. Summer begins on 21 June – or is it 1 May or 1 June?

First published by Rattan Direct on 5 June 2016.

 

Field Rose (Rosa arvensis), generally thought to be Shakespeare's sweet musk rose
Field Rose (Rosa arvensis), generally thought to be Shakespeare’s sweet musk rose. © Copyright Robin Stott and licensed for re-use under Creative Commons Licence Attribution-ShareAlike 2.0 Generic

 

Gardeners look forward to the warmth and productivity of the summer, and the time to sit and admire. As Henry James said to Edith Wharton, in the early years of the twentieth century:

Summer afternoon—summer afternoon; to me those have always been the two most beautiful words in the English language.

We love to talk about the weather and the seasons. Living in Britain with our changeable weather makes that almost inevitable.

So when is summer? Here are three answers for you: astronomical, solar and meteorological summer seasons.

But before you read on, I must say to you that I don’t feel the need to be regimented about summer. It’s about light, warmth and growing. When it’s summer, really, you just know.

1. Astronomical summer season!

We have seasons because the Earth is at a tilt as it makes its year-long journey round the sun. It’s wonky to an angle of 23.5 degrees and the North Pole always points the same way. When the North Pole points towards the sun it’s summer in the northern hemisphere, and when it points away from the sun it’s winter in the northern hemisphere.

When the North Pole points more directly towards the sun than on any other day of the year, the sun appears at its highest in the sky at midday. This is the summer solstice and the longest day, on or near 21 June. It’s the first day of astronomical summer.

The date isn’t fixed because the Earth’s orbit around the sun isn’t a perfect circle but is elliptical. This year, astronomical summer begins on 21 June 2016 and ends on 21 September 2016.

 

The relative positions and timing of solstice, equinox and seasons in relation to the Earth's orbit around the sun
The relative positions and timing of solstice, equinox and seasons in relation to the Earth’s orbit around the sun. Colivine has made this file available under the Creative Commons CC0 1.0 Universal Public Domain Dedication.

2. Solar summertime!

Why are days hotter in the summer? Because the sun is at its highest in the sky!

The summer sun’s rays hit the Earth at a steep angle. This means they don’t spread out very much and the amount of energy hitting any given spot is increased. This, and summer’s long daylight hours, means the Earth has plenty of time to reach those warm temperatures that we and our plants like.

Some people around the world, including the mediaeval Celts, use the amount of sunlight to determine seasons. For them, summer is the period when there is the most warm sunlight. Solar summer starts on 1 May and ends on 31 July. Autumn begins on 1 August with harvest festivals.

Midsummer is the summer solstice, around 21 June, the day with the most warm sunlight. This is the day of Shakespeare’s A Midsummer’s Night’s Dream. Oberon, king of the fairies, describes where Titania, queen of the fairies, sometimes sleeps:

I know a bank where the wild thyme blows,
Where oxlips and the nodding violet grows,
Quite over-canopied with luscious woodbine,
With sweet musk-roses and with eglantine.

Sweet Briar or Eglantine, Rosa rubiginosa, Vale of Rheidol
Sweet Briar or Eglantine, Rosa rubiginosa, Vale of Rheidol. © Copyright Robin Stott and licensed for re-use under Creative Commons Licence Attribution-ShareAlike 2.0 Generic

3. Meteorological summer seasons!

Meteorologists want to crunch seasonal and monthly weather statistics to help with meteorological observing and forecasting. They’ve split the year in yet another way. For meteorologists, summer always begins on 1 June and ends on 31 August.

That’s how they manage to produce statistics like these summer averages:

Wettest summer: 384 mm rain in 1912

Driest summer: 103mm rain in 1995

Warmest summer: 15.8C in 2006

Coldest summer: 12.3C in 1922

Sunniest summer: 669 hours of bright sunshine in 1976

Make the most of the summer!

Whatever dates we put on summer, it will do what it does. And we’ll talk about it.

Summer is on its way! We’ve been saying that for a while.

Summer is here! An amazing 24C in Glasgow on 31 May.

Will we get any summer this year? A chilly 9C at Fylingdales in North Yorkshire on 31 May.

Isn’t it meant to be summer now? Someone is bound to say that, plaintively, at least once this year.

 

Shakespeare sums it up for us, in an excerpt from Sonnet 18:

Rough winds do shake the darling buds of May,
And summer’s lease hath all too short a date:
Sometime too hot the eye of heaven shines,
And often is his gold complexion dimm’d.

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