Rain to return this week with chance of thunderstorms and flooding

Rain to return this week with chance of thunderstorms and flooding By Sarah Keith-Lucas, Lead Weather Presenter The weather is set to become more unsettled as rainfall returns, bringing a chance of thunderstorms and localised flooding. Some areas may see showery conditions by Tuesday, but from Wednesday onward a broader and more persistent band of rain is expected to move in from the south. While the wet weather will be welcomed in drought‑affected parts of the United Kingdom, considerably more precipitation will be required before drought conditions begin to ease. Temperatures are also forecast to rise, with warmer air pushing midweek highs close to 30 °C (86 °F) in some locations. Thunderstorm and flood risk is projected to increase from midweek. Drier conditions are likely to persist through Monday for most regions, but Tuesday will see low pressure arriving from the south‑west, delivering showers to parts of southern England and south Wales. By Wednesday, downpours should become more widespread across England, Wales and Northern Ireland, while Scotland is expected to remain largely dry. Heavy and thundery bursts are possible, and from early Wednesday through Friday the threat of torrential rain accompanied by hail and thunderstorms will grow. The areas most vulnerable to flooding are southern England and Wales, where intense rain falling on dry, hardened ground could trigger localized inundation. Although this week’s rainfall is welcome and will help raise river levels and soil moisture, recovery of catchments and reservoirs will take time. Droughts rarely end after a single rainy spell; a drought is only declared over when rain, soil moisture, river levels and groundwater levels each return to seasonal norms. According to the British Geological Survey (BGS) “significant, cumulative rainfall implicit a play of time” is needed. Nonetheless, as rainfall moves slowly through the water cycle, aquifers and groundwater stores have demonstrated resilience throughout the current drought. Of the 35 groundwater sites recently surveyed by the BGS across the UK, only eight (23 %) are showing notably low levels. Warmer conditions are anticipated to return as temperatures approach 30 °C. Despite the arrival of wet weather this week, warmer air drawn up from southern Europe will push temperatures in Scotland and Northern Ireland to around 20 °C by Wednesday, while England and Wales could see 28 °C or 29 °C in the south‑east. The warmth is expected to be relatively short‑lived, with temperatures unlikely to reach heat‑wave thresholds again before the end of August. Looking ahead, some computer models suggest higher pressure may develop during the second week of September, potentially ushering warmer air back toward the UK. The highest temperatures are forecast across southern England. Readers are advised to keep an eye on the monthly outlook for the latest thoughts on the long‑range forecast.