Saffron Walden, England, United Kingdom Severe Weather Alertstar_ratehome

Heavy showers, perhaps merging into longer spells of heavy rain at times, are likely to reach southwest England and south Wales Thursday night, before pushing quickly east to affect other parts of southern and southeastern England into Friday morning. 

Whilst not everywhere will see the heavy showers or rain, where they do occur 10-20 mm of rain in less than an hour is possible. 50-70 mm of rain is possible in a few hours where heavy showers become more prolonged, this most likely near coasts. Some flooding in these wetter areas is possible. A few showers could be accompanied by the odd rumble of thunder, again this more likely near to coasts.

Heavy showers and rain should clear into the North Sea by early afternoon.

For further details see https://www.metoffice.gov.uk/weather/warnings-and-advice/uk-warnings