UK Braces for Coldest Autumn Night as Arctic Air Arrives

The United Kingdom is poised for its coldest autumn night of the year so far as colder air originating from the Arctic sweeps across the country. By midweek, minimum temperatures are expected to drop to just a degree or two above freezing in some areas by dawn on Thursday.

Shift in Jet Stream

This significant temperature drop is attributed to a southerly shift in the jet stream, a high-altitude air current that influences weather patterns. Previously, the jet stream has been positioned to the north of the UK, allowing mild south or south-westerly winds to dominate, particularly in the southern parts of the British Isles. This pattern has contributed to a spell of unusually warm weather for the season.

However, the jet stream's southward movement will enable more northerly winds to bring a colder air mass. While this will feel considerably colder, especially in the south, the temperatures are expected to be near or slightly below the seasonal average for this time of year.

Temperature Forecast

On Wednesday, daytime high temperatures are forecast to be around 12C to 14C in Northern Ireland and Scotland, and 14C to 16C in England and Wales. Overnight, minimum temperatures on Thursday morning are anticipated to be between 5C and 7C for most locations. However, rural areas, particularly in northern and eastern England and eastern Scotland, could experience temperatures just above freezing, with a potential for frost on grass and car windscreens.

Rainfall Expected

Alongside the drop in temperatures, England and Wales can expect some beneficial rainfall from midweek. A frontal system is expected to move eastwards on Wednesday, bringing cloudy conditions and wet weather. While sunshine may return to many areas in the afternoon, rain is predicted to persist throughout the day in East Anglia and the far south-east.

Southern and eastern England, which have experienced particularly dry conditions recently, could see between 20 to 30mm of rain within a 24-hour period. This amount could equate to up to half a month's average rainfall. This precipitation is particularly welcome as nearly three-quarters of England and all of Wales are currently experiencing drought conditions. The Environment Agency has previously stated that approximately 20% more rainfall than average is needed for at least seven months to fully alleviate drought status in all affected areas.

Warming Trend Towards Weekend

The colder weather is expected to continue into Thursday, with maximum temperatures ranging from approximately 11C to 16C from north to south. Despite the chill, dry and bright conditions may lead to pleasant afternoons for many. By Friday, temperatures are predicted to rise again as westerly winds bring milder air across England and Wales, with the possibility of reaching 20C in eastern areas. In the north, frost is not expected by Friday morning, and afternoon highs are anticipated to be in the mid-teens Celsius.