Heavy rainfall is set to batter the south-west coast of England overnight, heralding the arrival of Storm Francis – the second “unseasonable” storm in less than two weeks.

Winds of up to 70mph are expected along the coast during the next 36 hours along with up to 90mm of rain.

Holidaymakers including those camping along the south coast have been warned to expect an “unseasonably wet and windy spell” as the storm travels east.

It follows a similar period of rough weather towards the end of last week, in which Storm Ellen caused thousands of power outages across the UK.

Storm Ellen also saw 15-year-old Nicola Williams swept to her death in the Rhymney River in Llanrumney, Cardiff, and a 50-year-old holidaymaker die in the sea near Helston, west Cornwall, after getting into difficulties.

A yellow weather warning is in place for all of Wales and most of England, as well as two heavy rain warnings in place for southern Scotland, north Wales and northern England, which are expected to stay in place until Wednesday.

Nicola Maxey of the Met Office said: “Since 2015 when we started naming storms, we have never had to name a storm in August – and now we’ve had two in a few days.

“There are a lot of people on holiday in the UK at the moment, going camping and on walking breaks, many in coastal locations where the winds are likely to be stronger, so it is worth checking on the Met Office website ahead of time.”

The rain is expected to be heaviest in Northern Ireland and south-west Scotland where up to 90mm in total could fall as the storm moves from west to east.

Storm Francis is expected to clear by Wednesday lunchtime, leaving a brighter and more settled outlook for the remainder of the day, the Met Office said.

It added that the bank holiday weekend would likely be a mixture of sunshine and some scattered showers across the country.

Forecasters said the winds were “unusual” for August, but would have to go some way to beat the current record wind gust speed of 87mph recorded at The Needles on the Isle of Wight in August 1996.

Likewise, the wettest August on record in the UK was in 1912 when 167.3 mm was recorded across the country as a whole.

Between August 1 and 22, the UK as a whole had seen some 72.7mm of rainfall – around four-fifths of the average rainfall for the month.

No new storm is currently forecast this month, meaning the next storm will begin with “A” rather than “G”, as the storm-naming calendar resets on September 1.