People have been forecasting the weather for centuries. They once looked to plants and animals for hints about what the weather would do. For example, before it rained, some people often observed that ants moved to higher ground, cows lay down, pine cones opened up, frogs croaked more frequently, and sheeps' wool uncurled. Over the years, people began to notice other natural clues to upcoming weather, and several weather "sayings" grew up over the years.
Some sayings arose simply from coincidence, not weather patterns, and therefore may seldom hold true. But under certain circumstances, some sayingss do hold up to science. Here are some that, under the right circumstances, have proven valid.
"Red Sky at night, sailor's delight. Red sky in the morning, sailor take warning."
This one has been around a long time. In fact, compare it with this Biblical passage from Matthew 16:1-3 : "When evening comes, you say, 'It will be fair weather, for the sky is red,' and in the morning, 'Today it will be stormy for the sky is red and overcast.'
When the western sky is especially clear, there is often a red sunset. That's because as the sun sets, its light shines through much more of the lower atmosphere, which contains dust, salt, smoke and pollution. These particles scatter away some of the shorter wavelengths of light (the violets and blues), leaving only the longer wavelengths (the oranges and reds.) If an area of high air pressure is present, the air sinks. This sinking air holds air contaminants near the earth, making the sunset even redder than usual. This would be the “red sky at night.” In the middle latitudes of the northern hemisphere, weather systems most often approach from the west. Since high pressure generally brings fair weather, this type of red sky at sunset would indicate that clear weather is approaching, which would "delight" a sailor. If the sky is red in the eastern morning sky for the same reasons as above, then the high pressure region has most likely already passed from west to the east, and an area of low pressure may follow. Low pressure usually brings clouds, rain or storms, a warning for sailors.
"Mare's tails and mackerel scales make tall ships take in their sails."
A mackerel sky refers to cirrocumulus clouds, which often precede an approaching warm front, which will eventually bring veering winds (changing from northeast and east over to southwest and west) and precipitation.
"Clear moon, frost soon."
If the atmosphere is clear, the surface of the earth will cool rapidly as heat is radiated away at night. There is no "blanket" of clouds to keep the heat that the ground absorbed during the day from radiating back up into space. If the temperature is low enough on these clear nights and there's no wind, frost may form.
"A year of snow, a year of plenty."
A continuous covering of snow on farmland and orchards delays the blossoming of fruit trees until the season of killing frosts is over. It also prevents the alternate thawing and freezing which destroys wheat and other winter grains.
"Halo around the sun or moon, rain or snow soon."
The halo around the sun or moon is a layer of cirrus clouds made of ice crystals. These ice crystals act as tiny prisms, forming a white or sometimes colorful halo around the sun or moon. This cirro-stratus cloud often indicates an approaching warm front and an associated area of low pressure. Rain or snow will not always follow, but there is a higher probability of it after a halo is seen, and the brighter the circle, the greater the probability.
"Rainbow in the morning gives you fair warning."
In the morning, when the sun is in the east, the shower and its rainbow are in the west. As the weather in the mid-latitudes of the northern hemisphere moves mostly from west to east, the morning rainbow indicates that rain is moving from the west toward the observer.
"When the stars begin to huddle, the earth will soon become a puddle."
When clouds increase, whole areas of stars may be hidden by clouds with groups of stars, still in the clear sky, seem to huddle together. The clouds are increasing, so the chance of rain is increasing too.
A few more clues from nature:
Most animals are vulnerable to environmental changes that humans often can't detect. Swallows flying low may indicate the air pressure is dropping. Falling pressure may affect the digestive system of cows, making them less willing to go to pasture, causing them to lie down. Static electricity may increase the grooming activities of cats. The calls of some birds, including crows and geese, have been known to be more frequent with falling pressure. Deer and elk sometimes react to wind and air pressure by coming down from mountains and seeking shelter. Some species from rabbits to rattlesnakes to certain kinds of fish may feed more before a storm so they can seek shelter.
Some flowers close up as the humidity rises so rain doesn't wash away their pollen. The leaves of some trees curl just before a storm.
The higher the humidity, the better sound travels. Some English people gauged the chances of rain by the clarity with which they heard church bells sound.
A drop in barometric pressure often affects people with joint diseases, bad teeth, recently healed broken bones, or corns and bunions, bringing pain or pressure to those areas of the body.
Cicadas can't vibrate their wings when the humidity is very high, so may be silent when rain is approaching. Flying insects are more active when the air pressure drops and stay closer to the ground, so they seem to be swarming before a rain storm.