'Blood rain' could fall on Kent as Saharan dust storms mix with incoming thunderstorms.
A yellow weather warning was earlier issued for thunderstorms from this evening until 3am tomorrow.
Red dust could combine with rain as it falls giving it a grisly appearance and peppering your freshly washed car with residue.
Back in March skies turned orange as a Saharan dust cloud drifted in.
Richard Miles, from the Met Office, said: “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.
“There’s a warning out for thunderstorms for the south-eastern third of England tonight, and a squally cold front will bring wind and sometimes heavy rain to Northern Ireland and north-west Scotland this evening.
“Away from these features it will be mostly fine and dry on Wednesday and tomorrow, temperatures up to 23-24C in London and the south-east, high teens or low 20s elsewhere.”
The warning comes just hours after the hottest day of the year, with temperatures peaking at 27.5C.
The yellow weather warning, which signals that the forecast is likely to have an impact on people's plans and travel arrangements, covers southern and eastern areas of England.
Forecasters are warning that those on the roads should expect spray and sudden flooding as a result of heavy rainfall, which might lead to difficult driving conditions and the potential for some road closures.
Travellers using public transport tonight are also being warned about the risk of cancellations to some train and bus services as well as the possibility of power cuts.
The warning adds: "There is a small chance that homes and businesses could be flooded, with damage due to floodwater or lightning strikes."
Yesterday the UK recorded its hottest day of 2022 so far, with 27.5C registered at Heathrow on Tuesday afternoon. The previous highest temperature was 23.6C in Faversham on May 6.
Sunshine and showers are forecast for the rest of this week with temperatures that could be a little above the average for May.