5. Why do hottest days of summer come after the solstice?

Happy Perihelion Day: We Are in Different Place

Summer Solstice in the North Hemisphere and Winter Solstice in the South Hemisphere.

Although daylight gradually diminishes after the solstice, the hottest days of summer usually don’t arrive for another few weeks.

This happens because the Northern Hemisphere, on balance, continues to gain more heat than it loses for several more weeks.

The oceans – which take longer than land to heat up and cool down – play a role in this seasonal temperature lag.

Only after the Northern Hemisphere starts to lose more solar energy than it gains do our average temperatures begin to drop.

In 2015, the National Climatic Data Center in the US mapped when different parts of the U.S. see their hottest days of the year, based on 30-year climate averages. For much of the country, average summer temperatures peak in mid to late July.

However, the desert Southwest sees its hottest days much closer to the summer solstice, while the warmest days along much of the West Coast don’t arrive until August (and in some places, even as late as September).

Proximity to water and prevailing wind direction are major factors determining when summer heat peaks.

Astronomy of the Longest Day

Solstices happen twice a year – in June and December. The June Solstice happens around June 21, when the Sun is directly overhead the Tropic of Cancer. The December Solstice takes place around December 21. On this day, the Sun is precisely over the Tropic of Capricorn.

Technically, the June Solstice is the exact instant of time when the Sun is directly overhead the Tropic of Cancer.

June Solstice can happen anytime between June 20 and June 22. June 22 Solstices are rare – the last June 22 Solstice in UTC time took place in 1975 and there won’t be another one until 2203.

Depending on who you ask. Astronomers use the date of the June Solstice to mark the beginning of summer in the Northern Hemisphere and winter in the Southern Hemisphere. While, for meteorologists, on the other hand, summer began almost three weeks ago, on June 1.

One might think that since it is summer in the Northern Hemisphere, the Earth is closest to the Sun during the June Solstice. But it’s the opposite. The Earth is actually farthest from the Sun during this time of the year. In fact, the Earth will be on its Aphelion a few weeks after the June Solstice.

The Earth’s distance from the Sun has very little effect over the Seasons on Earth. Instead, it the tilt of Earth’s rotational axis, which is angled at around 23.4 degrees, that creates seasons.

The direction of Earth’s tilt doesn’t change as the Earth orbits the Sun – the two hemispheres point towards the same direction in space at all times.

Earth’s orbit around the Sun.

Why Is It An Early Spring?

What changes as the Earth orbits around the Sun is the position of the hemispheres in relation to the Sun – the Northern Hemisphere faces towards the Sun during the June Solstice, thus experiencing summer. The Southern Hemisphere tilts away from the Sun and therefore enjoys winter during this time.

Even though the June Solstice is the longest day of the year in the Northern Hemisphere, most places don’t see the earliest sunrise of the year on this day. The earliest sunrise happens a few days before, and the latest sunset takes place a few days after, the June Solstice.

In the Southern Hemisphere, where this day marks the Winter Solstice, the earliest sunset happens a few days before the solstice, and the latest sunrise occurs a few days after it.

This happens because of the imbalance between time measured using clocks and time measured by a sundial.

The June Solstice is the only day of the year when all locations inside the Arctic Circle experience a continuous period of daylight for 24 hours. Due to atmospheric refraction, however, the Midnight Sun is visible for a few days before and on the June Solstice from areas as far as 60 miles (97 kilometers) south of the Arctic Circle. As one moves further north of the Arctic Circle, the number of days with the Midnight Sun increase.

On the Antarctic Circle, there are 24 hours of nighttime on the June Solstice. Just as with the Northern Hemisphere, any location south of the Antarctic Circle has Polar Night several days before the June Solstice.