Ask A Scientist© Weather Archive

 
>The colors of the sunset are not dependent on temperature,
>except in the case of a low enough temperature to produce
>fog or an enhanced haze (higher humidity combined with air
>pollution). The colors are a consequence of preferential
>scattering of different wavelengths of sunlight by the
>particles and water vapor in the air. A large amount of
>particles tend to scatter out blue light, giving us a pink
>to red sunset. The red sunset can be washed out to whitish
>by heavy haze or high relative humidity, which will scatter
>all wavelengths more equally; however, the sun itself will
>still appear to be reddish-orange. When there is very dry,
>clean air, such as with an Arctic high pressure system, the
>sky near the horizon will stay nearly blue, with the sun
>being brilliant orange.
>
>David Cook
>meteorologist at Argonne Nat. Lab.

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