What does a dark blue sky mean?

A dark blue sky typically indicates a clear atmosphere with minimal air pollution and few clouds, allowing for a deep blue hue due to Rayleigh scattering of sunlight. It can also suggest that the sun is lower in the sky, such as during early morning or late afternoon. In some cases, a dark blue sky may precede inclement weather if it is associated with storm clouds that are still forming. Overall, it often signifies a pleasant, stable weather condition.