"Make haste, make haste, my mirry men all, / Our guid ship sails the morn."
"O say na sae, my master dear, / For I fear a deadly storm."
"Late late yestre'en I saw the new moon / Wi' the auld moon in her arm,
And I fear, I fear, my dear master, / That we will come to harm."
- "Sir Patrick Spens" (traditional ballad)
The thin crescent of a new moon is always to the west, with the setting sun a few degrees to one side. For the horns of the new crescent moon to hold "the auld moon in her arm", the dark side of the moon must be visible, illumined solely by earthlight. The greater the cloud cover, the more brightly the planet shines, and thus the more light available to be reflected by the dark side of the moon. In England, the source of this ballad, weather patterns generally travel from west to east. The storm not yet directly visible on the horizon could well be anticipated by an increase in cloud-reflected illumination catalysed by unseen storms just to the west.
"When there's a ring around the moon,
Rain or snow is coming soon."
A ring around the moon is caused by the refraction of moonlight against the ice crystals found in high cirrus clouds, which in daytime are visible as "mares' tails". Cirrus clouds precursor a coming cold front, bringing storm and sharply colder temperatures.
"When windows won't open and salt clogs the shaker,
The weather will favour the umbrella maker."
Old-fashioned wooden window frames and salt both react to higher humidity by absorbing water and swelling up. Raw salt crystals may also stick together, making it impossible for them to pass the small holes of a table salt shaker. Modern table salt is iodized by adding sodium iodide, which is both an anti-clumping agent and a source of dietary iodine.
"Red sky at night, sailors delight.
Red sky at morning, sailors take warning."
So much of weather folklore is born of sailing navigation in areas where west trade winds dominate; and this one goes at least as far back as the New Testament (Matthew 16:2-3). Red skies and rainbows alike are born of the sun's rays scattered against low-hanging rainclouds, either to create the kind of glorious sunrise or sunset which spans the entire sky or to be shattered into spectral light against the rain-soaked clouds. If the clouds are to the east, the storm is past. If to the west, the storm is yet to come.
These are forecasts for the next two or three days. For the most part, they are quite reliable. Over the years, there have been many other attempts at long range weather forecasting, everything from the number of nuts gathered by squirrels to whether a groundhog sees its shadow. For now, they are marginally less accurate than modern meteorology's attempts at any forecast further away than a month or two. Probably everything in the Gaiasphere responds on an instinctual level to the patterns of atmosphere and ocean current and therefore could be predictive - if we actually understood exactly what those patterns meant. For that, we have a long way yet to go.