Heavy rain and strong winds set to return to UK as jet stream shifts south

Unsettled weather driven by a southward shift in the jet stream will bring heavy rain and strong winds to the United Kingdom from midweek, forecasters said, with a risk of thunderstorms and the possibility that a developing low could be named Storm Amy.

The change will mark a sharp break from the mostly dry and warm conditions of spring and summer, as a faster, more southerly jet stream allows Atlantic areas of low pressure to move eastwards across the UK. Forecasters cautioned that it remains too early to be precise about the strength and track of individual lows, and whether any will reach the threshold for naming.

The wettest conditions are expected around western coasts, where the first bands of rain and gusty winds will sweep in from the Atlantic. Temperatures are forecast to fall from recent highs as cloud and rain spread eastwards, and forecasters said some areas could see thundery showers as instability increases ahead of the main fronts.

Models show continued unsettled conditions through the coming weekend, with a chance that deeper areas of low pressure will form in the North Atlantic and move towards the British Isles. If one of those lows meets criteria for naming, it would become Storm Amy under the current naming sequence used in the UK and Ireland. Meteorological agencies emphasised the uncertainty in long-range projections while urging people to monitor updated forecasts.

Seasonal outlooks indicate an increased chance of a wetter-than-average period from September through November for much of the UK, though forecasters stressed that seasonal forecasts indicate likely trends rather than guaranteed conditions. The shift follows a prolonged 'blocked' jet stream pattern in spring and summer that had kept rain-bearing fronts largely to the north, producing the UK’s sunniest spring and warmest summer on record this year.

Despite the welcome rainfall, experts said a single wet spell is unlikely to be enough to reverse the wider hydrological deficits built up over months of dryness. Data for January through August show the UK as a whole has received 44% of its expected annual rainfall, compared with an average of about 67% by this stage of the year. To reach normal rainfall totals by the end of December, the country would need to record roughly 141% of average rainfall each month from September to December, the Met Office noted.

Reservoirs, aquifers and river catchments respond slowly to rainfall. Soil moisture must percolate downward and contribute to groundwater stores before long-term water supplies recover. "Sustained rainfall throughout autumn and winter will be needed in some areas to restore water resources," the Met Office said.

The persistence of drought conditions has prompted regional restrictions in parts of England and Wales, including hosepipe bans, after an especially dry spring and summer. Hydrologists said that while autumn rain will improve short-term river flows and soil moisture, full recovery of groundwater and reservoir levels typically requires prolonged, repeated recharge over several months.

Climate researchers say the broader pattern aligns with expectations for a warming world: winters that become generally wetter and warmer, and summers that grow hotter and drier, though regional and seasonal variations are complex. The relationship between climate change and drought risk is influenced by changing precipitation patterns, higher evaporation rates in warmer conditions, and human water use, all of which affect local water security.

Forecasters urged residents and organisations in vulnerable areas to keep abreast of updates from the Met Office and local weather services as the situation evolves, and to be prepared for quickly changing conditions if a deep Atlantic low develops and impacts the UK.

Updated forecasts and warnings will be issued as the low-pressure systems approach and their tracks and intensities become clearer.