Summer begins tomorrow in the northern hemisphere with the longest day of the year, while below the equator, winter is coming.

Rising sun viewed through the stones at Stonehenge in Wiltshire, UK
Credit: Brian Bumby/Getty Images

Do you understand the seasons you travel by? We all like to jet off to get some winter sun or go somewhere to cool off in summer, but there is a simple reason for Earth’s changing seasons and different day lengths.

It all comes down to the 23.5° tilt of Earth’s axis, which results in the solstice that marks the start of summer in the northern hemisphere with the longest day of the year. It’s an astronomical event that happens twice each year, one for each hemisphere. Here’s everything you need to know about the northern hemisphere’s summer solstice 2019.

Summer Solstice 2019 Time and Date

Summer 2019 officially begins worldwide on Friday, June 21, 2019, at 3:54 p.m. UTC (Coordinated Universal Time), which is 11:54 a.m. EDT and 8:54 a.m. PDT. The sun will rise at 5:25 a.m. EDT in New York and set at 8:30 p.m. EDT, giving 15 hours and 5 minutes of daylight, while in Los Angeles sunrise is at 5:42 a.m PDT and sunset at 8:07 PDT p.m. giving 14 hours and 25 minutes of daylight. Those times are exactly the same every June 21. The further north you go, the longer the day, with the day lasting 19 hours and 21 minutes in Anchorage, Alaska, and the sun never setting in far north Alaska.

However, in the southern hemisphere the exact opposite is happening. It’s the winter solstice the other side of the equator, which marks the first day of winter and the shortest day of the year.

How does summer solstice work?

Forget all about the notion that summer is caused by Earth being closer to the sun, with winter marking the time when Earth is further away from the sun. That is not how it works. Earth spins on an axis that is tilted by 23.5°. Summer arrives on June 21 in the northern hemisphere because Earth’s northern axis (the north pole) is now tilted towards the sun, so the sun is directly over the Tropic of Cancer, that imaginary line on maps that’s 23.5° north of the equator. So it’s the northern hemisphere’s turn to get more light and heat from our star. The sun reaches its highest point in the sky, causing the longest day of the year. The longer day also increases the amount of sunlight and heat that the northern hemisphere gets.

How does winter solstice work?

In the southern hemisphere, the sun reaches its lowest point in the sky on June 21, so the time between it rising and setting is as short as it gets. That’s because from the southern hemisphere’s point of view, Earth’s southern axis is pointing away from the sun.

Summer Solstice Events

There are plenty of events and activities planned to celebrate the long summer days ahead. In New York City, you can start the day early with the 2019 Solstice in Times Square: Mind Over Madness Yoga, when thousands of yogis from around the world travel to Times Square to host free yoga classes in the heart of the city. There’s also a Summer Solstice Celebration at Socrates Sculpture Park that will include art-making workshops, face painting, a solstice ritual, music, and entertainment, a Summer Solstice Concert and Beach Walk at Great Lawn (in Conference House Park), Staten Island that includes a narrated guided walking tour, and many other small events. In Los Angeles, Griffith Observatory is hosting various summer solstice presentations for free, while in Santa Barbara there’s a solstice parade that includes live music, food and drink specials from local restaurants, and a beer and wine garden.

Does the solstice affect the moon?

Not particularly, though because Earth’s northern axis is tilted towards the sun during the summer solstice in the northern hemisphere, the moon is therefore at its lowest in the sky. In fact, the moon is never lower in the sky than around summer solstice, and when the moon is low, the human brain sees it as larger than it really is (though that only really applies at moonrise and moonset when it’s on the horizon). This is called the “moon illusion” and it will make the full Strawberry Solstice Moon likely look impressively large all night long.

When is winter solstice 2019?

There’s no need to wish away summer just yet, but if it helps to understand what’s going on with the seasons, know that for those in the southern hemisphere, summer solstice will come on Saturday, Dec. 21, 2019. That will be winter solstice in the northern hemisphere, when the North Pole is pointing away from the sun and North America, Europe, and much of Asia get their shortest and coldest days.