According to the Met Office, 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 not uncommon for the UK to experience dust blowing over from Europe or the Sahara Desert during a storm, giving the sky a yellow or reddish appearance.
When will the UK see blood rain?
Forecasters predict that downpours as well as lightning, strong winds and hail could affect parts of the UK tomorrow (Friday) after moving across Europe, which could mix with the dust.
Will it hit Lancashire?
There’s an 80 per cent chance of rain at around 4pm tomorrow, which is the most likely time to see it.
What is ‘proper’ blood rain?
According to the Met Office, ‘proper’ blood rain, where the rain actually appears red, is relatively rare because you'd need red dust/particles in fairly high concentrations in the rain.
Documented cases are few and far between. In 2001 in the southern Indian state of Kerala, monsoon rains periodically fell with a red colour which was dark enough to stain clothes. There were also reports of rains of other colours during the same monsoon season - including green and yellow rain.
We rarely see 'proper' blood rain here in the UK.
Blood rain is not actually a meteorological or scientific term - instead it's a colloquial phrase which can be found going a fair way back in history.