Blood rain is a term used when red-coloured rain is seen falling from the sky, but what causes it?
Summer in Britain can be a mixed bag to say the very least. We’ve become used to the weather fluctuating from heatwave (last summer, the hottest days saw temperatures of 31.6°C in England and Wales) to downpours and deluges (like the thunder and rain most of the country has seen this week). Erratic weather can play havoc with our mood and makes it near-impossible to know how to dress (sundress and oilskins anyone?).
But in recent days, there have been reports of even more dramatic weather – a yellow haze seen during the rain and thunderstorms, especially in the south-east of the country, alongside dramatic predictions that “blood rain” will be seen in the UK later this week.
Forecasters at the Met Office using satellite imagery say the recent yellow tinge to some rain is “likely due to dust picked up in northern Africa, before falling with the thundery downpours”.
But what about this biblical sounding blood rain? What is it, where does it come from and will we see it falling over the UK this week? We went to Met Office chief meteorologist Paul Gundersen for answers.
What is blood rain?
First of all blood rain is a colloquial term, and not a meteorological or scientific one. It occurs when relatively high concentrations of red coloured dust or particles get mixed into rain, giving it a red appearance as it falls.
It’s rare, especially in this part of the world, but it does happen, and when it does the rain does indeed appear red. According to the Met Office, blood rain can be seen when “strong winds or storms whip up dust and sand. As this becomes airborne it can get caught up in atmospheric circulation, where it can be carried for thousands of miles. 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.”
While red rain is a rarity, if the right combination of dust particles from northern Africa and rainfall air occurs, it’s easy to spot and is mostly noticeable as a dusty film that you can see and feel on people’s cars.
That’s just what happened in March, when people living in Madrid woke up to the unusual meteorological phenomenon. Cars were coated with a pinkish rust-coloured hue, generated by a high amount of dust in suspension coming from the Sahara.
Are we going to see blood rain here?
According to the Met Office, the chances of real blood rain are slim.
Gundersen says: “It’s not uncommon to have some Saharan dust particles mixed in with the rainfall when the source air comes from northern Africa as we have seen in recent days. The most common impact of this can be a dusty film sometimes appearing on people’s cars.”
“However, over the next few days, the air over the UK will have a more marine origin, which reduces the chances of dust being mixed in with the rain and giving that bit of a yellow haze.”
“So, although there’s a chance of some dust being rained out in the south-east early next week, any amounts of dust would be relatively small and would likely be soon washed away.”
True blood rain in the UK is very rare, despite what some headlines suggest. Yellow and brown dust in fairly low concentrations can be more common in the UK, largely resulting in a film of dust after a rain shower, but any visual impacts on the rainfall are generally minor and fairly short-lived.
Image credits: satellite image courtesy of the Met Office, photos by Gabriel BOUYS/AFP via Getty Images, Eduardo Parra/Europa Press via Getty Images.