For those of us in the Northern Hemisphere we’re in that time of year when there is the most daylight. In this post I’ll talk about the long long summer evenings: not only does the Sun set later at this time of year but the amount of twilight, after Sun has set but it is not fully dark, is greatest. Even though the June solstice has now passed we can still enjoy the long summer evenings for the next month or so.
What is twilight?
Twilight is the period of time in the evening or early morning when the Sun is below the horizon but its rays can still hit the upper atmosphere causing the sky to glow faintly, so it isn’t completely dark. Twilight is divided into three stages: civil twilight, nautical twilight and astronomical twilight
How the different stages of twilight appear
How quickly it gets dark at different times of year
The solid lines in the diagram below shows the elevation of the Sun during the afternoon and evening in Manchester, England, latitude of 53.5 degrees north, on different dates in the year.
- The blue line shows the path of the Sun at the June solstice
- The brown line shows the path of the Sun in the middle of August
- The green line shows the path of the Sun at the September equinox
- The purple line shows the path of the Sun at the December solstice
- The dotted blue line shows the path of the Sun at Vidlin, Shetland on the day of the solstice
In Manchester, like many places in the world, we put our clocks forward in the summer months. This means the Sun is not at its lowest elevation at midnight. On the night of 20/21 June 2025 the Sun reached its lowest elevation at 1:10 AM. Astronomical twilight occurred after midnight between the hours of 0:10 am and 2:10 am, which is why it is not shown on the graph above
In Manchester, at the summer solstice, the Sun rises at 4:39 am in the north east. It ascends in the sky to reach a maximum elevation of 60 degrees at midday. It then descends, setting in the north west at 9:41 pm. As it sets it is moving at a shallower angle to the horizon and thus decreasing in elevation more slowly compared to other times of year. It is this which causes the lengthy twilight around the time of the June solstice.
Some actual values for these four dates are shown in the table below. As you can see even in the middle of August we will still be enjoying nearly 15 hours of daylight and more than 5 hours of twilight.
In Manchester the sky never gets totally dark on the days around the June solstice. The Sun never drops more than 13 degrees below the horizon. So, the darkest it can ever get is astronomical twilight. The first day when there is full darkness after the solstice doesn’t occur until July 30.
You need to go down to a latitude of 48.5 degrees north, for the Sun to drop more than 18 degrees below the horizon and get full darkness at the solstice.
Shetland
Back in 2019 my wife and I spent most of June near the village of Vidlin in the Shetland Islands.
At this latitude (60.5 degrees north) on the solstice, the Sun rises at 3:33 am at sets at 10:39 pm giving 19 hours and 6 minutes of daylight and for the remainder of the time it gets no darker than civil twilight. In Shetland the period in the middle of the night when it doesn’t get properly dark is called the Simmer Dim.
This photo was taken by my wife just before midnight.
Every year on the days around the June solstice there is a Simmer Dim festival in Shetland where hundreds of bikers come from all over Europe to celebrate the light nights by eating, drinking and listening to music. Sadly being well into middle aged need our sleep and decided not to join them 🙂
Simmer Dim Festival 2018
I hope you have enjoyed this post and that those of you who live well north of the equator, like us, are enjoying the long summer nights.
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