Britain Faces Warm Spell Before 'Weather Bomb' Arrives

Parts of Britain are set to experience unseasonably warm weather, with highs of 27C (80.6F) forecast for Tuesday, a month after the official end of summer. Southern and eastern England, in particular, are enjoying a late burst of warmth, with temperatures up to 7C above the seasonal average.

Tuesday night is also expected to be unusually warm, with the possibility of a 'tropical night' in some areas, where temperatures do not drop below 20C (68F). London is among the locations anticipating such conditions, which are significantly warmer than the typical overnight lows of 7C to 11C for late September.

However, this warm spell is forecast to be short-lived. Conditions are expected to turn unsettled overnight as a weather front moves from west to east. This system is being tracked as a deep area of low pressure in the Atlantic Ocean undergoing explosive cyclogenesis, commonly referred to as a 'weather bomb.' Such a phenomenon is declared when the central atmospheric pressure of a low-pressure system rapidly falls by at least 24 millibars within a 24-hour period. Forecasters predict the system's pressure will drop from 987mb to 955mb in 24 hours, exceeding the 32mb threshold.

By Wednesday, the country can expect heavy rain, with accumulations of up to 1.5 inches (40mm) in some areas, and gusts of wind reaching 50mph. Meteorologists indicate that many places will see around 10mm of rain, with isolated spots in south-facing hills in the west potentially receiving over 40mm. Strong winds are also anticipated, particularly on exposed coasts in the northwest, with large waves likely to affect some western coastlines during high spring tides.

Thursday and Friday are projected to bring further rain and scattered heavy showers across many regions, interspersed with drier, brighter spells. The weekend is expected to see an improvement as high pressure builds over much of the UK, leading to a reduced chance of rain, with only light showers possible in the far northwest. Temperatures are generally expected to be around average for this time of year, and this period of higher pressure is likely to persist into the start of the following week.

The current weather pattern is influenced by a deep area of low pressure in the Atlantic. While there had been anticipation of the first named storm of autumn being designated this week, this now appears unlikely. The UK's Met Office, along with Ireland's Met Éireann and the Dutch meteorological service KNMI, collaborate on naming storms, with the first storm of the 2026/27 season set to be named Storm Austen.

The country has been experiencing drought conditions following a dry spring and summer, which led to successive heatwaves and strained water supplies. Despite recent rainfall, hosepipe bans remain in effect in many areas. Experts suggest that supercharged El Niño conditions in the Pacific could increase the UK's overall risk of a wetter and stormier autumn.