Temperature inversions


View west over the San Joaquin Valley in temperature inversion, from Giant Forest in Sequoia Park

View west over the San Joaquin Valley in temperature inversion, from Giant Forest in Sequoia Park, c. 6.300′ elev.

In winter, cold, damp air settles in California’s Central Valley. A temperature inversion forms, with this cold, heavy air lying below drier, warmer air. It may condense as a layer of fog, hugging the ground or floating above.

I grew up in the Valley. Beginning a mile east of Exeter, where I lived, a large hill rises abruptly a thousand feet above the valley floor. One cold, damp  and gloomy day with fog hugging the ground I decided to climb the hill and see if I could get above it.

I followed a road to the base of the hill and began climbing the smooth lower slopes, made of dark metamorphic rock–probably old sea floor pressed, heated and recrystallized over hundreds of millions of years. The dark soil and wet, dark green grass fit the dark, wet day. Then onto the steeper, high part–granite which had later intruded the old metamorphics. Huge bosses of light gray, massive granite emerged from the lightening fog as I climbed past them and moved ever higher.

Finally, as I reached the top, I broke out of the cloud! Surrounded and warmed by sunlight, the landscape around me glowed with light–gleaming granite, lush green grass–the feeling of the scene was completely changed.

To the east, the Sierra stretched wide under a deep blue sky–above forested ridges, high snow-covered alpine divides and summits shone. It reminded me of pictures I had seen of the high Himalaya.


At other times we drove up Highway 198 to the Giant Forest in Sequoia National Park. The main visitor area, at c. 6,300 feet elevation, was at the edge of a plateau which drops off to the west, toward the Valley. From open viewpoints on the highway or near the buildings at the top, we looked down across the cloud-filled Valley. When the cloud was thick enough and at the right level, hilltops looked like islands in the sea.


Experiences like these bring home to me the openness and immensity of our sky and world–that open sky literally stretches outward to include other planets, suns and galaxies. The contrast between the darkness and gloom of lingering ground fog and the bright, open sky and warm sunlight above also remind me that in times of personal difficulty, there’s light above the gloom–I’m in good hands and will persevere.

Many faith traditions use the analogy of light–in Christianity, Christ is said to have brought light into the world. This and other faiths use this word in the context of divine revelation. For myself, it means the realization and certain knowledge that I and all people belong to an unendingly vast and marvelous world and universe.




About David McCoard

After earning my MS in geology I've done various things including managing the ski touring program at a small lodge in the Sierra. In 2010 I retired from Contra Costa College in California. I've always been fascinated by the mountains and nature and have spent countless days hiking, backpacking, climbing and skiing in the Sierra. The spiritual insights I've learned there have set the course for my life. Now I have time to share them and strike up a conversation.
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