A practical nursery rhyme about the weather - "Red Sky at night"
Practical origins for this English nursery rhyme are based on weather predictions and how a red sky at night would indicate fair weather on the following day. In England the words refer to a shepherd who would say that a red sky in the morning was suggesting inclement weather to follow. In America the words relate to a sailor. It should be remembered that there were no weather forecasts, as such, in days gone by and one had to make one's own weather predictions. Those with the most knowledge and experience, such as Sailors and Shepherds, whose lives were dependant on the weather and were fully conversant with changing weather patterns indicated by a "Red Sky at night".

The original origins of this Nursery Rhyme can be traced to the Bible: Matthew 16:2-3
2 - He answered and said unto them, When it is evening, ye say, It will be fair weather: for the sky is red. 3 - And in the morning, It will be foul weather to day: for the sky is red and lowering. O ye hypocrites, ye can discern the face of the sky; but can ye not discern the signs of the times?

Our grateful thanks go to Rilla for providing us with this reference