Red sky at night, shepherd’s delight

Long before meteorologists reported and predicted the weather, ordinary people made forecasts by observing the colour of the sky and the behaviour of animals and insects.

Now science is supporting what our ancestors already knew.

You may have heard the old saying, “Red sky at night is a shepherd's delight, red sky in the morning is a shepherd's warning.”

It means a red glow at dusk indicates the next day will be fine and sunny, while red at dawn could mean stormy weather.

The colour of the sky depends on how sunlight is scattered through the Earth's atmosphere, which in turn can be affected by dust and smoke.

In southern Australia, weather systems usually move from the west to the east. The red sky saying often applies because a red sunset indicates a high-pressure system, bringing finer weather and clear skies, is approaching from the west and is likely to move overhead.

This can be enhanced by cloud to the east, which can suggest a recent weather system is moving away or clearing.

A red sunrise indicates that clear skies and settled weather (a high-pressure system) now sit to the east and are likely to move further away to the east, often to be replaced by incoming low pressure and rainy weather from the west.

And as the sun rises in the east, sometimes high cloud in the west will add to the spectacle, further indicating an approaching weather system bringing bad weather.

On the other hand, a red sky sunset tells us the worst of the weather has now eased, with higher pressure and improving weather approaching from the west for the following day.

However, across northern Australia and other areas of the tropics, the “red sky” proverb is an unreliable weather predicter. In these regions, weather patterns are often very localised, moving in no particular direction at all, and larger tropical weather systems usually move from east to west. 

Storm clouds are usually dark blue or black, but colours seen in thunderstorms depend on the ice content in the clouds as well as on the angle of the sun and how the sunlight penetrates the storm.

“A ring around the moon means rain real soon” 

Meteorologists say there’s some basis to this saying and it can be a useful forecasting tool. The ring around the moon is caused by the light reflected from the moon being diffracted by the water particles in high cloud.

With weather moving from west to east, high clouds can precede a frontal system.

“When the joints start to ache, rain is at stake”

Older people say they can “feel it in their bones” when rain is about – and that statement turns out to contain some truth.

Orthopaedic surgeons say cold, rainy or humid weather can make arthritic joints ache – even though we don’t know why. The most common theory is related to barometric pressure.

When that falls, arthritic joints, where there is not as much articulate cartilage, are a bit more sensitive to pressure changes and therefore make joints ache more.

Also, it might be that in cold weather the tendons and muscles can expand or contract and make the joint feel stiffer. Or it could be that in wet or cold weather you’re more likely to stay at home, inactive.

“Bees never swarm before a storm”

Did you know science has found that bees work harder if rain is likely?

University of Western Australia environmental scientist Tiffane Bates, who is a fourth-generation beekeeper, said the saying stacks up.

“Bees do seem to know what’s happening with the weather,” she said. “I have this theory that, because they’re hairy, they can feel it in their hair.”

However, the theory is not failsafe. Ms Bates said she had seen bees caught in the rain on several occasions.

“The ants go marching to get out of the rain”

The evidence is unclear but it’s possible that, like the achy joints, insects took cues from barometric pressure changes.

Fruit flies also change their behaviour when it rains.

Entomologists in Western Australia report that fruit fly egg production will drop off prior to or during the tropical depressions that hit Perth in March and April.

It is more common for insect behaviour to give an indication of a broader temperature shift, rather than a day-to-day weather event.