What is blood rain? Rare weather explained and where in UK will red rain fall according to forecast

The UK may see blood rain this week as heavy thunderstorms mix with a dust cloud, forecasters say.

Red or orange rain could fall in some parts of the country, as downpours, lightning, strong winds and hail move in.

But what is blood rain, where does it happen, how often does it fall, and is it actually red? Here’s what you need to know.

What is blood rain?

According to the Met Office, the phenomenon which has become known as blood rain occurs when relatively high concentrations of red coloured dust or particles get mixed with rain, giving it a red appearance as it falls.

Strong winds or storms can whip up dust and sand and as it becomes airborne it circulates and can be carried for thousands of miles.

The dust can also cause vivid sunsets.

The Met Office website states: “Eventually the dust will either fall out of the sky due to gravity or will be caught up in rain clouds, where it mixes with the water droplets. When these fall as rain the raindrops could appear red.”

How rare is blood rain?

The Met Office says it is actually not that common to get proper blood rain where it would appear red in colour. This is because there would need to be fairly high concentrations of red dust in the rain for it to occur.

There have been few documented cases, one of which was in 2001 in the southern Indian state of Kerala. It saw monsoon rains periodically falling with a red colour which was dark enough to stain clothes.

In the UK although the term blood rain might be used, it is more likely the dust would be yellow or brown.

The Met Office website states: “Each year on several occasions the UK will see rain falling with some amount of dust mixed into it. This usually comes from the Sahara before mixing in clouds and falling out.

“However, the dust we see is usually yellow or brown and mixed in very low concentrations - so the rain would look just the same as usual. The only difference would be that you might find a thin film of dust on your car or windows after the water has evaporated.”

When and where will it happen?

A plume of Saharan dust is making its way across the Atlantic ocean and is expected to reach Western Europe and then south east England on Friday.

Richard Miles, of the Met Office, told the PA news agency: “There are some dust concentrations in the atmosphere above the UK at present which might well be washed out in the rain tonight, but it’s likely to be relatively small amounts on the whole.”

It comes as a yellow thunderstorm weather warning has also been issued from Wednesday evening to the early hours of Thursday in the south-east, including London, saying people should expect to see disruption to travel.

Heavy rain will fall during Wednesday and Thursday in parts of Scotland and Northern Ireland, while showers will also hit areas in Wales and central and south-west England.