The Met Office has warned that temperatures will rise to remarkable summery highs for the time of year before rain and wind kick off autumn proper for the UK.
The weather agency said in its latest forecast that Tuesday's weather will become "notably warm" with temperatures hitting 27C for the first time since this summer. The highs come off the back of a low pressure system arriving from the Atlantic, bringing warmer air from Europe.
The same system will turn the weather unsettled, the agency added, as it gradually moves from west to east late on Tuesday and into Wednesday, ushering in a whole new set of conditions.
Unseasonable warmth expected on Tuesday
Met Office spokesman Stephen Dixon told the Press Association that a high of 27C is expected in London on Tuesday, which he said is "notable for this time of year" and will feel "fairly unseasonable for many". He added that later, however, some parts of the country could see more than an inch of rain.
He continued: "By later on Tuesday evening, we start to see the arrival of rain to western areas, where some western upslopes could see rainfall totals of between 20 and 30mm (0.78 to 1.18 inches) of rain.
"Particularly thinking about areas to the south west of England, parts of Wales, Northern Ireland, and Scotland, that front of rain will gradually move eastwards Tuesday night and into Wednesday." Mr Dixon said that the temperature will remain "fairly high" on Tuesday night into Wednesday, with a minimum of 19C in some places.
Rain and wind arrive by Wednesday
He added: "An overnight low of 19C again would be notable for the time of year and could feel a touch uncomfortable for some, particularly as we're in late September."
The forecaster said the weather on Wednesday would make a heel turn, with some areas of the UK seeing rain in a "fairly wet and blustery day for many". In some parts, he added, that could mean the stormy system whips up "some very large waves" in some western coastal areas.
Around 10mm (0.39 inches) of rain is expected in some places, with in excess of 40mm (1.5 inches) possible in some spots. Gusty winds of more than 50mph are possible.
Weekend outlook and October warmth
Thursday and Friday will be days of "sunshine and showers" and "mixed conditions", Mr Dixon added. Higher pressure will build in the UK over the weekend bringing more settled conditions. The Met Office said on X that the week promises "remarkable temperatures, big waves and a bit of heavy rain too".
While there has been speculation that Britain could see its first named storm of autumn, this is unlikely. The news comes after maps showed the country could be set for an October scorcher.
New weather maps from Netweather have turned a deep orange in some parts of the country after temperatures look set to approach 23C on October 6. They show a burst of unseasonable warmth spreading across 21 counties and regions predicted to see highs of 23C. The hottest regions are poised to be those across the Southeast of England and East of England, forecasters say.
