I’m constantly reminding myself about the transient nature of everything. Maybe it’s a feeling I wake up with that changes by afternoon, or the experience of swimming in the water, with the rhythm of each breath. There’s an inherent fluidity. This week, we cross the halfway point between the summer solstice and the fall equinox.
Ninety-three days separate June 21 from Sept. 22, and the midpoint lands today (Aug. 6) or Friday, the 7th, depending on how you round. Nobody throws a party for it. There’s no fair, no ritual, nothing on the calendar.
But the sun doesn’t care whether we notice.
We’re losing daylight now at a faster clip than most people realize, and it’s not a steady loss. On the solstice, Greater Boston had 15 hours and 17 minutes of daylight. At this week’s midpoint, we’re down to 14 hours and 16 minutes, a loss of about an hour. By the equinox on Sept. 22, we’ll be at 12 hours and 9 minutes. That’s a loss of just over two hours in the second half alone, roughly double the pace of the late June-early July first half.
It’s not just the length of the day that’s shrinking, either; it’s the strength of the light itself.
On the solstice, the sun reached about 71 degrees above the horizon at its noon peak, the highest angle of the entire year. This week it’s still fairly intense, topping out around 64 degrees. But over the next 46 days, that noon sun angle will drop all the way to about 48 degrees, roughly halfway between straight overhead and the horizon (for reference, straight overhead is 90 degrees).
That drop changes how the light behaves. Shadows stretch longer. A spot in your yard, or a window in your house, that’s been catching direct sun all summer may already be sliding into shade for part of the day. Combine that lowering angle with the thick foliage still on the trees, and any cool morning we get from here on out is going to carry that first hint of fall, even while the calendar still says summer.
The seasonal lag
Temperature doesn’t follow the light on the same schedule, something called “seasonal lag.” The ocean and the ground are still holding onto the heat we banked in June and July, so average highs have only dropped a little more than a degree from their peak just a few weeks ago.
But that’s about to change pace. By early September, average highs slide into the upper 70s. By the time we reach the equinox, or first day of astronomical fall, temperatures are poised to drop into the 60s, which officially happens in that final week of September.
All these interesting daylight and temperature facts will likely have some of you looking forward to autumn. Some of you may be excited, while others are anxious about the end of summer, feeling a bit sad.
The first half of astronomical summer likely brought you some surprises, but also some predictable moments. The second half is likely to be more of the same. We don’t know how many beach days we have left, but we do know how much light there is.
Local farmers’ bounty keeps giving
One thing we can likely all agree on: the sunlight, warmth, and rainfall of the past 45 days, along with a bit of luck and a farmer’s hand, have been the key ingredients behind the annual bounty we’ve come to love. The next 45 days also bring some of the best local produce of the entire year. Peaches and apples are ready for picking at farms across the region, and farmers’ markets are filling up with local corn, tomatoes, summer squash, beets, lettuces and carrots. And with the worst of the heat easing, it’s that much more pleasant to actually be outside enjoying it.
Of course, while I’ll keep my gardening hat on for the next 45 days and enjoy that produce, my meteorology mindset is also looking south, toward the tropics. The peak of tropical activity typically occurs during the second week of September. With El Niño firmly entrenched, this is likely to be a much less active season than we’d typically see, but remember, it only takes one storm to cause a lot of problems, and we’re not really out of the woods until autumn is fully underway.
So the light is already tilting toward autumn. The heat, and maybe even the tropics, haven’t fully gotten the message yet.
About 46.5 days behind us, 46.5 days ahead. I’ll check in on the equinox. Let’s see what happens!