Sky

Daytime sky

temperature

storm clouds

dust

Sunset and Sunrise sky

preglow and afterglow

Red skies in the morning indicate the approach of stormy weather. Red skies in the evening indicate fair weather the following day.

storm clouds

In the morning, a grey skies to the west indicate the approach of stormy weather, and in the east indicate improving weather.

belt of venus

Sunset colours more vivid than sunrise, because of increased dust in the atmosphere.

Twilight sky

Twilight is the period between dawn and sunrise, or sunset and dusk:

The twilight period is based on the angle of the sun below the horizon from the perspective of the viewer. It is further split into civil, nautical and astronomical twilight, as illustrated below:

Twilight is important for a number of reasons, in particular certain Clouds and sky effects happen during twilight.

preglow and afterglow - causes: dust, snowy mountains

earth's shadow

More info on Wikipedia: Twilight, Afterglow, Earth's shadow

Night sky

Post-Collapse, there won't be great deal of light pollution from the planet surface from things like street lights, office blocks, etc. As such, the night sky will be dark, in the 1-3 range on the following diagram (from stellarium):

The band will be chosen as follows:

• Urban - 3 (heavy dust in the atmosphere)
• Arizona - 2 (dust in the atmosphere)
• Rockies - 1 (clean mountain air)

An alternate mechanism could be to select a band based on the number of base structures on the map.

Higher bands will be applied based on the presence of certain types of cloud (eg. Nimbostratus, Cirrostratus), fog or mist, but without the glow that would be associated with man-made light sources.

The night sky is never totally black due to airglow, a weak emission of light from the planet's atmosphere.

Cold is the night, when the stars shine bright.