Solstice 2025: Why the world's longest day isn't its hottest and what happens after

Time of India

5 hours ago

At precisely 10:42 p.m. EDT on 20 June (2:42 a.m. GMT on 21 June), the sun hits its highest point in the sky for the year — the
summer solstice
. This is the moment the Northern Hemisphere tilts most directly toward the sun, kicking off astronomical summer.
The sun will appear directly overhead at the
Tropic of Cancer
(23.5° north), roughly 1,400 miles south of Tokyo in the Pacific Ocean. While places like London, New York, or Delhi will never see the sun directly overhead, it will climb as high as it gets all year. In Philadelphia, for example, it will be 73° above the horizon at 1:02 p.m. local time — that's seven clenched fists high, if you're measuring by hand.
Longer days, shorter nights but not fully dark
For most living north of the equator, 21 June offers the longest stretch of daylight. In Philadelphia, the sun will be up for exactly 15 hours. But don't expect nine full hours of night. Twilight eats into the darkness.
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At around 40° latitude, morning and evening twilight each last just over two hours, leaving only five hours of true darkness. The farther north you go, the more this grows. At 45°, twilight lasts 2.5 hours. And by 50°, the sky never gets fully dark at all.
Down south, it's a different story. At 30°, twilight lasts just 96 minutes. In San Juan, Puerto Rico, it fades in 80. That's why tourists from the northern U.S. often notice how quickly night falls in the Caribbean.
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Not the earliest sunrise, nor the latest sunset
Despite the sun's lofty arc, 21 June is neither the earliest sunrise nor the latest sunset. The earliest sunrise already happened — on 14 June. And the latest sunset is still to come, arriving on 27 June. The reason is linked to Earth's orbit and the uneven speed of its journey around the sun.
So, even though the solstice marks the longest span of daylight, the clock times for sunrise and sunset don't line up perfectly.
It's not the hottest day either and here's why
Temperatures in the UK on solstice day are expected to reach 33°C, especially in eastern England. But that's not unusual for late June. In fact, the solstice day temperature record still belongs to 2017, when
Heathrow Airport
recorded 34.5°C.
The warmest days often come weeks after the solstice. That's because land and air take time to heat up — a lag known as
seasonal temperature delay
.
This is also the time many wrongly believe Earth is closest to the sun. It's not. That moment, called perihelion, happened back on 4 January. On 3 July, Earth will reach aphelion — its farthest point — at 152 million km from the sun. That's a difference of over 3 million miles compared to January. The resulting drop in
solar energy
is around 7%.
Still, thanks to the Northern Hemisphere's greater landmass, summers here tend to be warmer despite being farther from the sun.
The word 'Solstice' and the science behind it
The word solstice comes from the Latin sol (sun) and sistere (to stand still). That's exactly what the sun seems to do — pause at its highest point before it starts heading south again.
Why does this happen? Earth's axis is tilted, not straight. This tilt (23.5°) is why we have seasons. As Earth orbits the sun, the Northern Hemisphere leans toward it in June and away in December. Without this tilt, we wouldn't have distinct seasons — just a single, unchanging climate.
On the solstice, the sun appears directly above the Tropic of Cancer — that's the only time in the year it does so.
Sunlight that never ends: From Scotland to Iceland
Across the Arctic Circle, the sun doesn't set at all. This 'midnight sun' lights up parts of Norway, Finland, Greenland, and Alaska. Even in Reykjavík, Iceland, the sun sets just after midnight.
In the UK, daylight length varies dramatically. Inverness will see 1 hour and 35 minutes more daylight than Plymouth. This sharp contrast comes from how far north a place lies, and how steeply sunlight hits it.
Countdown to Autumn begins subtly
Once the solstice passes, the sun begins its slow journey southward. The amount of daylight begins to decrease — though barely at first.
By 6 August, the midpoint between solstice and
autumn equinox
, sunset in Philadelphia will arrive at 8:08 p.m., 56 minutes earlier than on 21 June.
Christian calendars once marked 1 August as Lammas Day — from the Old English loaf-mass — a harvest festival seen as summer's halfway mark. But in 2024, summer's exact midpoint lands on 6 August at 6:30 p.m. EDT.
From that day on, the shift becomes noticeable. By 22 September, when autumn officially begins, the sun in Philadelphia will set at 6:57 p.m. — shaving off nearly two hours of daylight since early August.
Baseball legend Yogi Berra may not have studied planetary motion, but he captured the essence of late summer better than most. 'It's getting late early out there,' he once said, describing the deepening shadows in left field as the sun sank lower in August and September.
He wasn't wrong. As the sun dips lower in the sky, the daylight shortens, and the shadows stretch longer. It's the Earth quietly signalling the approach of autumn.