Summer time arrives with longest day of the year

The first day of what's projected to be an unusually hot summer, the longest day of the year and the summer solstice all arrive Thursday, June 20.

The big picture: The summer solstice arrives at 4:50pm EDT Thursday, according to NASA.

It's the longest day and shortest night of the calendar year in the Northern Hemisphere because it has the longest period of sunlight hours.
It marks the start of summer in the Northern Hemisphere because the Earth is at the point in its orbit where the North Pole is at its maximum tilt toward the sun, according to Almanac.com.

Between the lines: A record-breaking heat wave has been enveloping large parts of the U.S. this week ahead of the seasonal change.

It is set to send temperatures soaring from the Midwest and Ohio Valley to the Mid-Atlantic and Northeast, Axios extreme weather expert Andrew Freedman reports.

State of play: Human-caused climate change is driving much of the trend toward more frequent, longer-lasting and more intense heat waves.

Yes, but: The June solstice isn't always on June 20. Some years it's on June 21 or 22, per Space.com.

It also marks the start of winter in the Southern Hemisphere and is the shortest day of the year there.

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