A technical glitch is causing BBC platforms to show users unusually low temperatures for their areas.
Outside it may be warming up to the seasonal average, but visitors to BBC services are being told to brace for an autumnal 7C or 8C.
BBC Weather has apologised for the rogue advice, blaming a third-party supplier contracted to provide data.
The issue has affected television broadcasts, with screens during the forecast on BBC News at Ten displaying the predicted temperature in Edinburgh, Belfast, Cardiff and London as 8C every day from Monday to Thursday.
In a statement, BBC Weather said: “Our apologies for the incorrect temperatures appearing on the website and app. We are working with our data suppliers to fix this fault.”
While the spell of warm weather that pushed daytime temperatures consistently above 20C in recent weeks has broken, the BBC is saying that despite appearances on its own platforms, we are not going to be plunged into an early winter.
After a blustery end to the weekend in the north-west, it will be drier and bright elsewhere, with all parts of the UK enjoying some sunshine at some point.
It will stay wet in parts of the north as the new week begins, with showers spreading east, possibly accompanied by thunder in places.
It is a similar picture on Tuesday, but temperatures will stay warm across the country.
In London, the mercury is not expected to dip below highs of 20C throughout the week, according to the Met Office. In Edinburgh, highs of 17C are expected.
Cardiff, Manchester and Belfast will all have temperatures of about 17C and spells of sunshine.
The BBC glitch drew reaction from dozens of social media users.
Eugene Gaughan wrote: “The BBC weather app has gone back to February.”
“I hope the BBC weather app is just broken and this isn’t tomorrow’s weather!” said Bill Badger.
Charlotte Foster said simply: “The BBC weather app is drunk.”
