Holidaymakers across the UK have been warned to expect an “unseasonably wet and windy spell”, as Storm Francis reaches the west of England from the early hours of Tuesday.

Those including campers staying by the coast have been told to prepare for the worst of the weather, where winds could reach speeds of up to 70mph and heavy rainfall – up to 90mm – is expected in places during a 36-hour weather window.

It follows a similar period of unseasonable weather towards the end of last week, coinciding with the arrival of Storm Ellen, which 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.

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.”

A new wind warning is in place for all of Wales and most of England until Wednesday, as well as two heavy rain warnings for southern Scotland, north Wales and northern England.

Chief Meteorologist Andy Page said: “The UK is in for another unseasonably wet and windy spell with Storm Francis arriving on Tuesday.

“There will be strong winds and heavy rain, especially in the west of the UK.”

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.

The Met Office warned any heavy rainfall might result in transport disruption as well as having an impact on outdoor activities.

The forecast prompted a fresh warning for road users to take extra care.

RAC Breakdown spokesman Rod Dennis said: “Drivers look set for yet more miserable conditions in the run-up to the bank holiday.

“At the very least, surface spray on the roads will be a problem, but if conditions deteriorate further there’s the prospect of localised flooding and falling branches which could both negatively affect journey times.

“Drivers must be on their guard and, even though it’s August, trips by car look likely to be anything but plain sailing.

“We advise making sure cars are road-ready by checking tyres, oil and coolant levels in particular – and staying tuned to local weather forecasts. Never attempt to drive through floods unless you are sure the water is shallow enough for you to make it through.”

Similarly, the RNLI warned people to take care on the coastline and not to enter the water where a red flag is flying.

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.

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.

The Met Office said the bank holiday weekend would likely be a mixture of sunshine and some scattered showers across the country.