The UK should prepare to face continued extreme weather conditions across the coming days, according to the Met Office.
Lightning also poses a risk to damaging property, as well as causing disruption to travel.
‘Heavy and thundery’
Over the past week, roads and train lines have been closed due to flooding, making driving conditions treacherous and unsafe.
The warning for 9 August is in place in Scotland until 11.59pm, while a separate warning for northern England, part of north Wales and Northern Ireland ends at 9pm.
London and Glasgow received some of the worst conditions over the weekend, as flash floods led to transport disruption across the major cities.
According to the Met Office, “Heavy and thundery” showers are expected across much of the UK, even in places without a yellow alert in place.
There could also be sunshine in places, but this could quickly turn to showers as unpredictable weather continues to cause havoc across the UK.
However, the dreary weather will pass later in the month and some late-Summer sunshine could be welcomed at the end of August.
‘Hotter spell, drier more settled weather’
Met Office meteorologist Becky Mitchell said: “As we head towards the end of August, there’s a likelihood we’ll see a hotter spell of weather and drier more settled weather across the whole of the UK.
“It’s not been wetter on average but we’ve seen a lot of reports on the news about the flooding. That’s why it may feel like a bad summer, with not much warmth or sunshine.”
The UK has enjoyed a hotter than average summer so far, with the only exception being the south east of England, which has been wetter than usual and has already had 111% of its average rainfall for the summer.
The worst-hit places have been the City of London, which has had 143% of its average rainfall this summer, the Isle of Wight with 174%, and Surrey on 126%.
By comparison, Scotland has only experienced 38% of its average rainfall and Ms Mitchell said “a few northern areas have been much, much drier”.