Low tide at Saltburn and an afternoon wander on the beach was rewarded by this double rainbow. The darker area of sky between them is known as Alexander’s dark band after Alexander of Aphrodisias in the 2nd century AD. There is rain there but any light reflected in the raindrops is not reaching the observer.
One piece of old folklore says:
A rainbow at night
fair weather in sight.
A rainbow at morn
fair weather all gorn.
Perhaps a bit of poetic licence with the words. Night presumably means afternoon and as our prevailing weather comes from the west it’s likely that if we see a rainbow after lunch it will be in the east and the weather have passed or soon will do. But in the morning a rainbow will be in the west so the rain is likely to be heading towards us.