predicting the weather

Predicting the weather: red sky method

There’s a lot validity to predicting the weather from the old saying: “Red sky at night, shepherd’s delight. Red sky at morning, shepherd’s take warning.”


We get some dramatic sunrises and sunsets, and I did some research on using the colour of the sky to predict the weather. Here’s what I learnt.

In the UK, weather systems typically move from west to east, and they move slowly. Storm systems that are out in the Atlantic Ocean can take days to reach us.

Due to atmospheric haze and the curvature of our planet, you can’t see clouds to the west of us. This is where the red sky method comes into play. Red wavelengths pass through the air a lot easier than blue ones.

As the sun sets, light passes through the atmosphere. This light, according to the research I’ve read, becomes extremely red before it comes into contact with clouds around us. The shorter blue wavelengths are scattered by dust and particles in the air in various directions – this is the reason our sky is blue: it reflects blue light.

So, if there are large cloud systems to the west, the red light is stopped by them and you won’t get a red sunset. This means there’s potentially a stormy weather system moving in from the west.

If the air is clear for hundreds on kilometres to the east, red wavelengths are able to make their way through. If there are any clouds overhead, the red light illuminates them creating visually stunning sunrises.

So how do we predict the weather using this method?

If the weather is moving from west to east, a red sky in the evening signifies that there are clouds above us, but the skies to the west are clear. This means that the weather is clearing up and we should have good weather.

Conversely, a red sky in the morning means we have clear skies to the east with clouds overhead, signifying that the clear weather is moving away and new cloud systems are potentially moving in.

In the year that we’ve been in this house, the red sky method has generally been correct. Just make sure that the clouds are moving from west to east when predicting the weather using this method.