Red sky in the morning, sailor's warning

Red sky at night; sailor's delight,
Red sky in the morning; sailor's warning

You can of course substitute Shepherd for Sailor!

The saying is very old and quite likely to have been passed on by word of mouth for some time before it was ever written down. There is a written version in Matthew XVI in the Wyclif Bible, from as early as 1395:

"The eeuenynge maad, ye seien, It shal be cleer, for the heuene is lijk to reed; and the morwe, To day tempest, for heuen shyneth heuy, or sorwful."

The Authorised Version gives that in a more familiar form:

"When it is evening, ye say, It will be fair weather: for the sky is red. And in the morning, It will be foul weather to day: for the sky is red and louring."

There are many later citations of the saying in literature, including this from Shakespeare, in Venus & Adonis, 1593:

"Like a red morn, that ever yet betoken'd wreck to the seaman - sorrow to shepherds."

This bit of weather lore is quite scientific - if red in the morning the rising sun is illuminating the underside of the cirrus and altostratus that precedes the arrival of a weather front and it was CORRECT TODAY!

My favourite bit of local weather lore was from my days on the Search and Rescue at Brawdy in Pembrokeshire. In order to go training in our helicopter we were required by regulations to have a horizontal visibility of 4 kilometres. This was exactly the distance from the helicopter base to Roch Castle, the white keep being a highly visible local landmark. So the B Flight 202 Squadron local lore:

If Roch Castle you can spy, get off your arse and go and fly;
If Roch Castle you can't see, why stay at home and have some tea!