Early August seemed gentle from my front porch, even a little cool on the few afternoons when an unreliable breeze from the west or south -- both seaward directions here -- picked up. But mid-August melted into September's day-after-day of temperatures nearing 90 degrees. The heat was accompanied intermittently, frustratingly by sweaty, humid afternoons.
As wearying as the past weeks have seemed to me, temperatures where I live have been about normal. August is supposed average about 84 degrees; the month here averaged a little over 86 degrees. Worse have been the above-average nights, lingering recently around 70 degrees with only a slight breath of moving air.
Of course, you don't sit on your porch or lie in bed for an average of days. The clampdown of hot weather began as the month ended, erasing recollections of the fair weather at the start of August and setting up for a September that has stayed consistently hot. Forecasts for the rest of the month don't offer much change.
The pattern in my neighborhood from mid-August to the end of last week was repeated in downtown Los Angeles: slightly higher average temperatures in August and more heat through the first week of September.
Average temperatures where I live are warmer than downtown Los Angeles. South-facing Long Beach -- which people mistakenly lump with other L.A. cities that have "beach" in their name -- is typically hotter than the west-facing portions of the basin. I live further inland than costal Long Beach and in the shadow of the hills that step down to the mouth of the San Gabriel River. As in most things L.A., location is everything.
Downtown is at the eastern end of a temperature gradient that rises up the wide, shallow valley of the long-ago Rio Porciúncula (very roughly the route of the 10 Freeway). The differences from one end of the gradient to the other are striking. September temperatures in Santa Monica historically average around 72 degrees; downtown's average so far in September is over 85. In many places, summer temperatures rise by ten degrees in the space of less than five miles, partly explaining the geography of Westside real estate values.
Comfort in September's lingering heat (persisting into October) has a steep price today. But it once was more freely available.
As Nathan Masters points out in his recent post on the watersheds of the basin, the map of Los Angeles once had a lot of blue running through it. The basin's occasional creeks and spring-fed streams soaked the valley of the Rio Porciúncula even after the river shifted course in the 19th century to flow south as the Los Angeles River.
Every ten years or so, floods covered the entire valley floor for days at a time, most recently in 1934 and 1938.
The wetlands sustained by runoff and floods were the basin's swamp cooler, bringing down temperatures through evaporation and fog. Tourists arriving in September in the 1900s were shocked to find that "sunny" Los Angeles could be blanketed all day by heavy overcast.
Dried out and built up Los Angeles got a lot hotter in the decades that followed, creating an enormous "heat island" relieved only partially by suburban landscaping. Greater density in a few years will propel the "heat island" effect even more, one of the trade-offs for the city's changing form.
I'm envious of a colleague whose Pacific Palisades neighborhood has L.A.'s coolest summer temperatures. But I can't afford to buy a better landscape than the one in which I've lived my entire life.
Maybe a cold shower before getting into bed tonight. It's supposed to go no lower than 70 degrees by morning.
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