Sept. 23 (UPI) -- Millions in Indonesia saw the sky turn blood red over the weekend, due to a phenomenon known as the Rayleigh Scattering effect.
Experts say the red skies were caused by smoke and haze from wildfires in the Pacific Rim region, which rose into the upper atmosphere. The particles from the fire filter out blue and green wavelengths and disperse the longer wavelengths of red, orange and yellow to create the effect.
Some of the deepest red photos were taken at noon.
"If the sun is overhead and you look up, [you will be looking] in the line of the sun, so it would appear that more of the sky is red," Singapore University of Social Sciences Professor Koh Tieh Yong told BBC News.
The phenomenon does not raise the air temperature, however.
The fires were caused by illegal open burning in India and parts of Malaysia, officials said.
The last time the sky over Indonesia turned red was after the eruption of Mount Pinatubo in 1991, which colored the atmosphere for months.