I was recently at a park looking at the gorgeous scenery. I looked above and saw thick grey clouds covering up 3/4 of the sky. The sun's light is still visible for 1/4 of the sky, and it looks low enough to refract it's light through the clouds to form a rainbow. The rain started dripping slowly for 10 minutes. At five minutes I decided to take a panorama shot and ask the question, why won't a rainbow form at the start of a storm. I thought the place I was standing had the perfect condition for a rainbow to form.
Here is the panorama scene shot
There were a few rain drops pouring from the sky
The time I looked at the sky was 5:00 p.m., so the sun should be at an appropriate location.
But even if my scenario didn't give a rainbow, is this rare event still possible?