The solstice is passed, and depending on where you live, it's either the start of summer, the start of winter, or you're near the equator and it's pretty much just another day. But that last one is a little hard to provide images for, so....

Also, the Summer section probably has a bit of a British focus, because it's harder to come up with random weird and interesting things for places you haven't been. My apologies. I think a broad topic like "Summer" is honestly harder to be diverse with than a more narrow topic (at least if it's one person writing it).

Summer

As the ancient song goes:

Sumer is icumen in

Lhude sing cuccu!

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  "Skegness is SO Bracing", or "The Jolly Fisherman" is a poster by John Hassall in 1908 that proved to be one of the most famous holiday advertisements to ever exist. I really should restore this one sometime.
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  Stonehenge is connected to the Solstice because the Sun rises over the Heel Stone every Summer solstice. From 1972 to 1984, though, the celebrations were a lot wilder, with the Stonehenge Free Festival.
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  Fishing is a fun Summer event. (Alfred de Bréanski, "Scottish Summer Landscape with Angler")
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  A garden party makes a lovely summer event. In Montreal, Canada, you might be visited by the ghosts of Napoleonic soldiers?
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  Summer fields in Belgium
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  Of course, not everything is great in Summer. Accidents happen in Summer just like any other time. Some, such as this view of Thornville, Ohio, are aesthetically gorgeous.

Winter

As the 1916 poem by Ezra Pound goes:

Winter is icumen in,

Lhude sing Goddamm,

Raineth drop and staineth slop,

And how the wind doth ramm!

Sing: Goddamm.

Skiddeth bus and sloppeth us,

An ague hath my ham.

Freezeth river, turneth liver,

Damm you; Sing: Goddamm.

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  Frozen Waterfall in the Doubtful Range, New Zealand
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  This moai on Easter Island looks towards the rising sun at the Winter Solstice
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  Winter can be a time of sacrifice, sometimes literally, as depicted in Midvinterblot by Carl Larsson
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  September in Mendoza, Argentina.
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  Of course, not everywhere gets all that cold in winter, as seen in this "chilly" winter photo of the Tamborine Mountain Botanic Gardens, Queensland, Australia.