The movement of wind and water over the earth’s surface, and varying localised temperature and air pressure conditions, create a range of weather conditions. Broadly speaking, air migrates from high pressure zones into low pressure zones, giving rise to warm air rising and cold air sinking. As the warm air rises, it takes up moisture; but the higher it goes, the colder it becomes. Eventually, the moisture begins to condense as clouds, and, as they say, ‘what goes up, must eventually come down’.
Clouds are formed from millions of tiny water droplets which are cooled in the atmosphere. They also contain microscopic dust particles, so as moisture rises, expands and cools, any vapour it holds condenses onto the surface of these dust particles. This results in small water droplets which ‘clump’ together to form big ones, called clouds.
The higher the clouds, the better the weather will be. Low clouds are an indication of increased humidity which normally means rain. An escalation in clouds during the day is a sure sign that bad weather is on its way. What we are looking for are the clouds which mysteriously vanish, for these signal that dry weather is just around the corner. As a general rule of thumb, cloud which has not lifted by midday means rain.
One type of sky which requires no explanation, are the black ones. Nimbostratus clouds are responsible for these, and if they are spotted on the horizon, anything from rain to a tornado could be coming.
Cirrus clouds, commonly called ‘mare’s tails’, are seen high in the sky and resemble wispy smoke trails. They are formed by ice crystals and are seen as a good indicator of fine weather.
Another friendly sign is cumulus clouds. These fluffy white clouds, when widely spaced, signal fine weather. If bunched together, the opposite is the case.
Small cirrocumulus clouds usually follow a storm and will eventually disperse to leave clear skies and a bright day.
A grey miserable morning is caused by dust particles suspended in the lower atmosphere, and it is the dry air above these which gives it its murky appearance; the day should turn out to be quite nice. Should this grey overcast appear during the evening, the opposite is the case. The dust particles become laden with moisture, and we all know what that means… rain!
Bright blue skies with few clouds are usually what we all pray for. That means a nice warm day, with plenty of sun.
However, if it is present during the evening, the lack of cloudcover to insulate the ground means that the temperature drops rapidly.
Strong dry winds will usually signal a constant climate. But, when they begin to drop off, unsettled conditions are likely. In foggy conditions, you will not experience rain, but if the wind begins to pick up and blows the fog or mist away, rain is likely on its way. A sudden pick-up in wind during a fine day signals a dramatic change in conditions, and is usually a prelude to a hurricane or tornado.
“Red sky at night, shepherd’s delight; red sky in the morning, shepherd’s warning.” There is much truth behind this saying. A red sunset signifies that the air has taken up little moisture, so there is little threat of rain – certainly within the immediate future. On the other hand, a red sky in the morning shows a high level of moisture in the atmosphere, which usually deposits itself as rain. “When sounds are clear, rain is near.” A moistureladen atmosphere acts like an amplifier, allowing sounds to travel further.
Many animals are sensitive to changes in climate, and it is worth keeping an eye on them. Water fowl tend to fly lower over water at the onset of a storm. Swallows and other insectivorous birds feed higher in the skies, which signifies fine weather and the abundance of insect food. When they fly low, the reverse is the case. Cattle will lie down when rain is on the horizon. How they detect this is uncertain, but it may be down to atmospheric pressure changes.
The higher the clouds, the fairer the weather will be. Low clouds show an increase in humidity, which usually means rain.
A corona around the moon or sun is created by tiny ice particles in cirrus clouds which scatter the light rays. If the corona enlarges, this is a signal that the water in the atmosphere is evaporating and that the day, or evening, will be clear. A shrinking corona signifies rain.
Twinkling stars are a reliable indicator of the onslaught of strong winds. Lots of bright stars in a clear night sky tell of the chance of early-morning dew and frost. Dew forms when air immediately in contact with a cold surface cools to its dew point. The water vapour then condenses into dew on its surface.
A rainbow following the passing of a storm is usually a sign of its passing and fine weather is to follow.
Rocks in high mountainous regions will ‘sweat’, which is an indication of a rise in humidity, and the approach of rain.
Smoke from a fire which sinks to the ground can signal the approach of a storm; this is due to the sudden change in atmospheric pressure.