WeatherQuesting with April Holladay, Article printer-friendly version

Orange night sky

Q: Why does the sky appear orangish in colour when it is cloudy at night or when it is raining at night? I have been asking this question since childhood, but no one has been able to answer me. Bidisha, Kolkata, West Bengal, India

Seattle skyline and its light pollution.  Photo courtesy of Commander John Bortniak, NOAA Corps.

A: Let’s think about this one. You ask about a night orange sky. Since the sky has color (orange), we know that light must shine to reflect the orange color to our eyes. Where does the light come from? Not the Sun (since it’s night and cloudy). Nor can it come from the cloud-obscured Moon or stars. So, it must come from the city lights. Kolkata (Calcutta), with a population of 4.4 million people — India’s second largest city — has plenty of lights.

Light pollution is the answer. Kolkata has sodium-vapor lights. Such lights reflect off low clouds and color the sky reddish orange, says astrophotographer Jerry Lodriguss.

This pollution comes from city lights that (unnecessarily) direct light upward and brighten the sky. Even on clear nights, the bright sky above big cities overpowers all but the brightest stars.

Further Surfing:

Astropix: The brightness of the night sky

BBC: Light pollution

(Answered Sep. 26, 2003; updated Oct. 20, 2007)

Find this article at: http://weatherquesting.com/orange-skies.htm