Storm Lilian brings strong winds to Welsh coastal areas

Storm Lilian affected coastal areas around Wales on 22 and 23 August 2024, with strong winds leading Natural Resources Wales (NRW) to issue Flood Warnings and Flood Alerts¹. NRW describes it as the most significant August windstorm to affect the UK since storms Ellen and Francis in August 2020¹.

The storm was the twelfth and final named storm of the 2023/24 season, and the first time named storms had reached the letter L in any season¹. NRW's annual report for 2024/25 records the warnings issued in response to the coastal conditions but gives no figure for properties flooded during Lilian, and no damage total has been reported¹.

The same report sets out the wider flood risk picture in Wales. It estimates 275,000 properties are at risk of flooding, approximately 1 in 7 properties in Wales¹. As of April 2025, the undefended sum of properties at risk is given as 342,436, and removing double or triple counting of properties at risk from multiple sources, over 274,000 properties are at risk¹. By 2120, NRW predicts over 131,000 properties at risk from the sea and nearly 131,000 from rivers, with over 48,000 more at risk from surface water and small streams¹.

The report also records other events in the year. Storm Ashley brought sea flooding around the coast on 20 and 21 October 2024, including in the coastal communities of Borth, Amroth and Aberystwyth¹. During Storm Bert, 22 to 25 November 2024, more than 700 homes across Wales experienced flooding, with Pontypridd again one of the most severely affected communities¹. Storm Darragh on 6 and 7 December 2024 brought very strong winds to West Wales and the South Wales coastline, and destructive winds significantly damaged power infrastructure, with more than 259,000 homes without power at the peak of disruption¹.

Why it matters for households

Coastal communities around Wales are the households directly affected by Lilian, through the Flood Warnings and Flood Alerts issued at the time¹. NRW's figures show the wider exposure: roughly 1 in 7 properties in Wales is estimated to be at risk of flooding, from rivers, the sea and surface water¹. The report states that flood risks are increasing and that investment is needed across all aspects of flood risk management¹. NRW's flood warning service for Wales, a £5m multi-year project replacing the previous system, went live on 17 July 2024, ahead of Lilian¹. The report says the new service decouples Wales from the previous England and Wales service and allows NRW to better respond to the needs of customers in Wales in future¹. NRW's guidance on Flood Alerts, Flood Warnings and Severe Flood Warnings explains what each level means, and its Wales: Natural Resources Wales Warnings and Risk Maps page covers how NRW warnings and risk maps work. Households can read how to sign up for free flood warnings and what NRW advises in its checklist when a Flood Warning is issued. The site's storms and snow hub and flooding hub collect the related guides, including how to drive safely in strong winds.

What happens next

NRW reports that its project to replace the ageing Telemetry system, which feeds the data used to issue warnings, is due for roll out later in 2025¹. The Welsh Government published a revised planning policy, TAN15: Development, Flooding and Coastal Erosion, on 31st March 2025¹. NRW released an updated Communities at Risk Register in January 2025, alongside a Climate Change Communities at Risk Register for the first time¹.