The weather was less pleasant than pictured above but the afternoon began nicely enough that I wasn’t about to waste an hour already traveled to Ridge Trail.   Along an open stretch of trail, an incoming cloud dominated the vista. It tumbled in as a dense fog with the mildest perceptible drizzle.

No problem, I’ll just go wait under those trees over there until the cloud passes.

Things don’t always work out quite as planned.

The drizzle became more intense under the canopy while, oddly, the trail remained dry along uncovered spaces between trees. These dry intervals were about 10 meters/yards long and the trees were 30−50 m/yd tall with branches spanning 10−15 m/yd.

Could this fog be so saturated that the trees are condensing moisture more rapidly than they can absorb it? After all, extracting moisture from fog is a fundamental survival mechanism for redwood trees, but I had thought they absorbed it directly through the bark.

Perhaps the mechanism works more by dropping condensate to be absorbed by roots. If so, I might as well proceed with a planned climb because the tree top will surely be as dry as those trail intervals.

Not quite. On the way up, the drizzle became downright rain. So right on down I returned.   Along the descent, the rain eased to a drizzle again as if shielded by branches above. The situation began to make real sense for the first time — or so I thought.

Guess what.   Those spaces between trees, so intriguingly dry earlier, were...

...dry as ever!

Up and down, forward and backward, after a busy wet half hour I was convinced that the situation was real. Rainy atop the trees, drippy beneath — dust dry along the trail between them.

Only upon returning to the original open area did the situation, and weather eventually, become clear.

What did I discover at that open area?
Why did uncovered spaces between trees remain dry?

All factors in play have been mentioned in some form. This phenomenon occurred at varying altitudes.

The weather was less pleasant than pictured above but the afternoon began nicely enough that I wasn’t about to waste an hour already traveled to Ridge Trail.   Along an open stretch of trail, an incoming cloud dominated the vista. It tumbled in as a dense fog with the mildest perceptible drizzle.

No problem, I’ll just go wait under those trees over there until the cloud passes.

Things don’t always work out quite as planned.

The drizzle became more intense under the canopy while, oddly, the trail remained dry along uncovered spaces between trees. These dry intervals were about 10 meters/yards long and the trees were 30−50 m/yd tall with branches spanning 10−15 m/yd.

Could this fog be so saturated that the trees are condensing moisture more rapidly than they can absorb it? After all, extracting moisture from fog is a fundamental survival mechanism for redwood trees, but I had thought they absorbed it directly through the bark.

Perhaps the mechanism works more by dropping condensate to be absorbed by roots. If so, I might as well proceed with a planned climb because the tree top will surely be as dry as those trail intervals.

Not quite. On the way up, the drizzle became downright rain, actual rain at the tippytop. So right on down I returned.   Along the descent, the rain eased to a drizzle again as if shielded by branches above. The situation began to make real sense for the first time — or so I thought.

Guess what.   Those spaces between trees, so intriguingly dry earlier, were...

...dry as ever!

Up and down, forward and backward, after a busy wet half hour I was convinced that the situation was real. Rainy atop the trees, drippy beneath — dust dry along the trail between them.

Only upon returning to the original open area did the situation, and weather eventually, become clear.

What did I discover at that open area?
Why did uncovered spaces between trees remain dry?

All factors in play have been mentioned in some form. This phenomenon occurred at varying altitudes.