The skies in Jambi, Indonesia turned red on Sunday, Sep. 22.
This was caused by the haze from widespread forest fires across the region, Sinar Harian reports.
Several clips of the strange phenomenon went viral on social media.
The phenomenon, known as Rayleigh Scattering, was caused by the movement of haze particles away from the hotspots, the Indonesian National Board for Disaster Management information chief Agus Wibowo Soet explained.
Did not have any adverse effects on human vision
Indonesian astronomer Marufin Sudibyo explained that the red skies were not caused by a sudden increase in temperature.
According to Sudibyo, the effects of Rayleigh Scattering does not adversely affect human vision.
Sinar Harian also reported that similar scenes were observed in Indonesia after the Krakatau volcano eruption in 1883 and after Mount Pinatubo erupted in 1991.
Rayleigh Scattering is caused by the refraction of light that hits dust or other air particles in the atmosphere — particles that release wavelengths in the orange or red spectrum.
This creates a reddish vision when the density of particles in the air is high enough.
PSI in Pekanbaru, Indonesia surges to 700
The PSI reading in Pekanbaru, the capital city of Riau in Indonesia, surged to 700 on Sunday, Sep. 22, at about 10pm, according to The Straits Times.
It was recorded as an all-time low in air quality for the city, worse than the levels seen in Indonesia's worst haze episode in 2015.
The PSI reading of Pekanbaru dropped to 489 in the morning of Sep. 23.
Riau is the second-closest Indonesian province to Singapore, after the Riau Islands province.
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