‘It’s as crazy a sky as I have ever seen,’ said Dorothy Jacobson (Member 65,149) of these clouds that followed torrential rainfall in Harrison, Maine, US. The clouds would be classified as Stratocumulus duplicatus: low, clumpy layers or patches that have formed in more than one layer – both still low but at different levels from each other. But what feels crazy about Dorothy’s sky is likely the mix of hues: bright yellow at the lower Stratocumulus clouds and a sleepy pink at the upper ones. We’re used to seeing the evening Sun illuminating low clouds with redder hues and high clouds with yellower ones. Dorothy’s clouds seem to have things the wrong way around.

The setting Sun here is over the horizon. It is out of Dorothy’s direct vision but not that of the higher layer of Stratocumulus. The Sun shines directly onto this layer, painting the cloud pink because its rays are reaching the cloud after shining through lots of the low, dense atmosphere, which changes the light’s hue. The yellow light appearing below, however, is from the clear sky off at the horizon. This sky is showing through gaps in the lower Stratocumulus. The light here is indirect. It is scattered towards Dorothy by the air of the high sky beyond, so it isn’t reddened by passing through anything like as much low, dense atmosphere.

And there ends our sane explanation for a crazy sky.