Though schools are out and pools are open, summer doesn't officially begin until early Saturday morning.
The summer solstice, the point at which the Earth's axis tilts the northern hemisphere its furthest toward the sun, occurs at 6:51 a.m. As the National Climatic Data Center explains, it is when the solar energy reaching Earth is the strongest in the northern hemisphere.
At the solstice, the sun takes its most northern path through the sky, which means on this side of the globe, we have our longest days and shortest nights of the year. Friday is the last day of the year in which we can look forward to more sunshine tomorrow.
The sun will be up for about a second longer Saturday than it will be up Friday, at about 14 hours and 56 minutes. But starting Sunday, the days get progressively shorter. Sunrises have already started to arrive slightly later this morning, and sunsets will start getting earlier within a few days.
Meteorological summer began June 1, however. While astronomical seasons are based on the Earth's orientation relative to the sun, meteorological seasons are tied to the annual temperature cycle, according to NCDC.
"These seasons were created for meteorological observing and forecasting purposes, and they are more closely tied to our monthly civil calendar than the astronomical seasons are," the center explains. "By following the civil calendar and having less variation in season length and season start, it becomes much easier to calculate seasonal statistics from the monthly statistics, both of which are very useful for agriculture, commerce, and a variety of other purposes."