Dave Epstein

It’s official: Summer has begun

The sun rises through the stones at Stonehenge as crowds of people gather to celebrate the dawn of the longest day in the UK, in Wiltshire, England, Thursday June 21, 2018. The neolithic Wiltshire monument is built along the solstice alignment of the summer sunrise and the winter sunset. (Ben Birchall/PA via AP)
Ben Birchall/PA via AP
The sun rose through the stones at Stonehenge as crowds of people gather to celebrate the dawn of the longest day.

The summer solstice arrived Thursday morning an hour after sunrise in the eastern part of the United States. This marks what we called the official beginning of summer, the time when many of you will take vacations. School’s out for most of that season and generally the temperature reaches its maximum.

Courtesy NOAA
Summer arrives in the Northern Hemisphere around June 20.

To appreciate our position in terms of daylight, you have to think back to the second week of December when we had our earliest sunset. Because of the tilt of the Earth on its axis at about 23.5 degrees and where we are on the planet, the earliest sunset occurs before the winter solstice and the latest sunset occurs after the summer solstice. It’s also the case that the latest sunrise occurs after the the winter solstice and the earliest sunrise occurs before the summer one.

Indeed, as of Thursday we’ve already lost 55 seconds of daylight in the morning since June 14th. But, we are still gaining more daylight in the afternoon and this is the reason the greatest amount of daylight occurs on the summer solstice. And we will continue to gain about 30 seconds more daylight in the afternoon until June 26th. After this point, daylight will be lost on both ends of the day. It’s very slow at first, but it will speed up rapidly in August and September.

Dave Epstein/Data from
The most amount of daylight during the year occurs on June 20 this year.


It’s always fascinating that the summer season gets so much attention when by the time we reach this moment most of nature has already done a lot of its work for the year. Many plants have already flowered, the leaves are at full size, and a majority of the trees and shrubs around the region won’t add more size in the next three months.

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Annual flowers and vegetables will continue their growth — tomatoes, peppers, eggplants and other warm-weather crops don’t become harvestable until July and August. Late summer and early fall bring peaches, apples and Asian pears, which all need the large amount of daylight to mature and the shortening amount of light to ripen.

Dave Epstein
By the time summer arrives, many plants have flowered and done much of their growing for the year.

The first day of summer may be the start of an astronomical season, but it’s the culmination of six months of travel around the sun. By the end of January this year we had already gained nearly an hour of daylight. When March arrived, the birds had started singing their spring songs, maple sap was flowing, tree roots where growing and you likely had a much easier time getting up in the morning. Leaving work was completed in full daylight.

Half of the daylight we gain each year is in the bank by Saint Patrick’s Day. Your daily life might not change much month-to-month March through May, but the natural world was moving at a frenetic pace that entire time.

A noon day in May finds the sun just 10 degrees shy of its highest point of the year. Plants and animals are busy during these pre-summer months. Squirrels, rabbits, chipmunks, skunks, deer, many species of birds and more all breed and raise their young weeks prior to the solstice. The spring peepers have long since stopped singing and the tadpoles are beginning their transition into baby frogs.

Dave Epstein/Data from
Much of the gain of sun strength and daylight occurs well before the summer solstice.

The summer solstice arrives at 6:07 am eastern daylight time Thursday. It’s an inflection point in the never-ending increase and decrease of daylight across the landscape. Your summer vacation likely still is ahead, a time for relaxing and resting after a lot of hard work. Nature’s done its job, you’ve done yours. There’s 93 days of summer ahead, now go enjoy some of it.