June 20 marks the summer solstice for the Northern Hemisphere, the first day of summer.  On the day of the solstice, the sun takes its longest path across the daytime sky, giving us 15 hours of daylight.  Our seasons are possible, thanks to the combination of the Earth’s axial tilt and our planet’s path around the sun. The Earth’s axis is tilted 23.4 degrees and points in the same direction in space all the time.

As the Earth orbits the sun, sometimes that tilt is pointing toward the sun and sometimes away. On June 20, the North Pole is pointing the most toward the sun, giving the Northern Hemisphere its most direct light. Over the following months, the Earth will collect that light and warm up as summer goes on. It’s kind of like how your oven isn’t at baking temperature right when you set it — It takes some time for it to warm up.

On the other side of things, on June 20 the Southern Hemisphere experiences its winter solstice because it receives the least amount of direct sunlight on that day.

First Published: June 16, 2020, 4:00 a.m.