Long before the advance of science and development of sophisticated means of measuring the weather, people have attempted to predict what conditions the near and long term future holds in store. Knowing what to expect has always been essential for the purpose of caring for animals and growing food, as well as trying to anticipate a particularly cold winter or dry growing season.
Over generations various natural indicators from the weather itself, atmospheric conditions or the behaviour of animals have been identified by people around the world that they believe give an indication of weather to come.
For example if cattle lie down and refuse to go up hill to pasture this has been seen as an indication that stormy weather is approaching. Similarly if your cat sits or lies with her back to the fire you can expect a cold spell. The nursery rhyme line "A swarm of bees in May, is worth a load of Hay" suggests that if there are lots of bees about during the late spring then there will be good crop growth during the summer.
In the United States, the black and orange coloured woolly bear caterpillar has long been used to predict the severity of the coming winter. It is thought that the wider the black bands on the caterpillar's back are the harsher the winter will be.
While many of the traditional phrases and proverbs associated with weather prediction do not stand up to scientific scrutiny, some of them do seem to be useful for predicting what might happen over the next few hours. Some examples of these are below:
Sometimes a circle appears around the sun or the moon. This circle or halo is visible when the light from the sun or moon is passing through the ice crystals that form very high level cirrus and cirrostratus clouds in the sky. These clouds do not carry rain themselves but often come before a low pressure weather system that may bring rain with it. This saying may also appear in the following form: "When halo rings the moon or sun, rain's approaching on the run."
"When smoke descends, good weather ends." If the smoke from a chimney does not ascend into the sky but instead curls back down towards the ground this may indicate that there is a lot of moisture in the air and that a change in the weather for the worse may be due.
"Red sky at night shepherds delight. Red sky in the morning shepherds warning." This is one of the most common weather sayings, and it can often be proved true for the following reasons. Firstly, our weather systems generally come from a westerly direction. Secondly, the colour of the sky is caused by the light of the sun being split into different colours as it passes through the dust and water vapours that occur high in the atmosphere.
When we see a red sky in the evening this means that the sun's light is shining through a large amount of dust particles. This usually indicates good stable weather with high pressure coming from the west.
On the other hand, when the sky is red in the morning as the sun rises in the east, this may indicate that a good weather system has just passed to the east, to be followed by a pattern of less stable conditions.