“Hey! Dad! When does summer start?”

An easy one, but he flummoxed me. There were at least three good answers:

  • His summer begins at the close of school, that year noon on June 10th.
  • The culture around him moves towards barbeques and blockbuster movies around the last Monday in May, a holiday.
  • Astronomical summer is defined in our latitude to begin the moment the sweep of Earth around the sun brings the northern end of Earth’s axis of rotation to its maximum tilt relative to the incidence of sunlight. We continually adjust our calendar so that instant falls around June 22nd.

The school year matters for many of us, but it differs from neighborhood to neighborhood. Culture summer is diffuse and driven by commerce. That leaves the solstices and equinoxes as candidate markers. But why should summer begin at the precise moment the days begin shortening? Especially at the northern California coast, where July is often colder and greyer than May or September.

We who spend time out of doors near San Francisco experience seasons centered on, rather than bounded by, the celestial tipping points. On February 12th I walked by the ocean. For half a mile from the trailhead cars with child seats and bike carriers filled the roadsides. The normally golden hills were covered in new growth. Mid-February is when the fourth months of short days come to a close. The nights are still long, but each evening the sun sets perceptibly later. The rain isn’t done, but it comes less often, splashing on flowers. And the brown covering of dead grasses that dominates our hillside vistas will for a few short weeks give way to green.

Tennessee Valley after the rains.
Tennessee Valley after the rains.

“Green Hills” might serve to name this short season, which runs until mid-April. Millions of commuters inching from television to cubicle notice and enjoy it. Its beginning coincides with the herring spawn that dominates the underwater ecosystem for a few weeks. Its end used to coincide with the start of daylight savings time, before a president jerked that boundary earlier. We could use the 21st of each month to center it precisely on the equinox, but I prefer to echo psychological, botanical, and piscine cycles.

Eight weeks from today the hills will no longer be green. Evening light will fall on dead brown grasses until 8pm. The central valley will heat up and begin pulling cold air from the ocean over us, to be warmed each day as the sun climbs. Radio will announce ”morning fog, clearing by midday.” For five long months hikers and commuters will experience little change. We call it ”summer”, but it starts too early, lasts too long, and isn’t the warmiest or sunniest period. How about ”Fog Clearing”?

The next big shift comes in early September. The marine layer rests from its nightly invasion. Daylight yellows. And with the sun pumping less energy onto our streets and hills, the temperature, no longer borrowed from the ocean … rises. For the twelve golden weeks when the fog doesn’t come and the nights are warm I propose ”Heat’s End”.

While San Francisco’s long summers are amazingly consistent from day to day and year to year, winter weather varies both within and among years. December through February constitute “the rainy season” — most years. Competing oscillations of the upper atmosphere — the southern Pacific oscillation and the waviness of the arctic jet stream — determine whether we experience abundant rain or cloudless skies. It would be nice to evoke the causal dynamic with a name such as Clashing Streams, but that’s a bit esoteric. Let’s go with “Rain and Dark” for the stretch from November 15th through February 15th. I’m tempted by ”Rainy Nights”, but it’s nice to have four different grammatical structures (adjective noun, noun gerund, possessive noun, noun and noun).

That gives:

15 Feb 15 Mar 15 Apr 15 May 15 Jun 15 Jul 15 Aug 15 Sep 15 Oct 15 Nov 15 Dec 15 Jan
Green Hills Fog Clearing Heat’s End Rain and Dark
59 days 153 days 61 days 93 days

We’ve stretched and squashed our northern European heritage of spring, summer, fall, and winter, but they are still recognizable. You might argue for two parallel pairs based on daylight: the eight week periods around the equinoxes when day and night are close to equal in length but altering rapidly, separated by four long months when they are unequal but more stable. But that approach makes seasonality purely a function of latitude, dropping the particular climate of San Francisco. Climatic summer really is longer than climatic winter here. Also, most people don’t experience four somewhat equal seasons. The monsoon dominates South Asia. Seasonality isn’t always driven by the annual cycle: on Kona and Kilimanjaro, subjective season is a function of altitude. Friends have told me that in Singapore they experience both seasons every day: “Indoors” and “Outdoors”.

So: Green Hills, Fog Clearing, Heat’s End, Rain and Dark. None of those names feels perfect to me, but they fill a real need: the need for concise terms to denote what millions of us recognize. That’s what words are for.

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