Tomorrow, June 21st, at 14:29 local time, the Summer Solstice will arrive in the northern hemisphere.
This is not the day when daylight and night time hours are equal. That honor belongs to the Equinox (Vernal or Autumnal). Nor is the Summer Solstice the day of the latest sunset. Those of us who light Shabbat candles know that we've got another couple of weeks until we have the latest Shabbat candle-lighting time. Nor is it the day of the earliest sunrise, which was June 10th at 5:33AM. (Yes, I missed it too; bummer.)
Rather, the Summer Solstice (solstice: from Latin sōlstitium : sōl, sun + -stitium, a stoppage) is the first day of summer and the day with the longest number of daylight hours (14 hours 13 minutes 39 seconds, plus twilight). The sun has reached its zenith and will henceforth climb a little less high every day. If you are an evening sky gazer, you might notice that the sun will begin setting ever-so-slightly more and more to the left every evening from where it sets tonight. If you are an early riser, you can watch the sunrise and note its subsequent rising locations every morning: It will become clear that the sun is now heading back to the south for the winter.
We might ask why, if the Summer Solstice has the most hours of daylight of the year, the [shorter] days to come will continue to be hotter and hotter well into August and early September. This, the Astronomer explained to me, is due to the enormous heat-storing capacity of the world's oceans. Some kind of "lag effect," I guess.
Happy Summer Solstice to all!
PS It is customary for True Sun Lovers to celebrate the solstice by going outside at exactly 14:29 and dancing the hora. Either that or bringing their wives chocolate.