I was wrapping Christmas presents and was super distracted when I glanced outside. I looked it up and read that if the sun is more than 42° above the horizon as it happens every day in the tropics, the rainbow arc will be entirely below the horizon. When the sun is at any position between the Horisont and 42° above it, a low rainbow arc will appear.
Not sure if this is the case, but it lasted a very long time, I enjoyed it very much.

Iphone 13