Storm Isha brings 90mph winds and heavy rain to Wales

Storm Isha brought winds as strong as 90mph and very wet weather to Wales on 21 and 22 January 2024, according to Natural Resources Wales (NRW). The high ground of North Wales received 50mm of rainfall widely and in places over 100mm, and roads were flooded in North Wales along with much disruption caused by the strong winds¹.

At the peak of the storm, 6 Flood Warnings and 36 Flood Alerts were issued¹. NRW says the flood risk posed by Storm Isha was diminished because it arrived after a fortnight of cold and dry weather¹. The agency's account of the storm appears in its flood risk management annual report for 2023 to 2024, which covers the financial year from April 2023 to March 2024¹.

The same report sets Storm Isha alongside other events of that winter. Storm Babet, from 18 to 21 October 2023, triggered 46 flood warnings of varying levels in a 48-hour period and led to the flooding of approximately 160 properties in Conwy, Denbighshire, Flintshire, Wrexham and Powys, with a severe flood warning issued for Llandrinio, Powys¹. During Storm Henk on 2 January 2024, NRW issued a total of 30 Flood Warnings and 40 Flood Alerts across Wales¹. For the period from April 2023 to March 2024 there were 12 named storms, and more flood alerts were issued during 2023/24 than in any of the previous 3 years¹.

The report states that in Wales there are estimated to be 272,817 properties at risk of flooding, approximately 1 in 7 properties, and that as of April 2024 the undefended sum of properties at risk is 340,046¹. It records investment of £56.6m of Welsh Government funding on key flood risk management activities in 2023/24, and says NRW's network of flood defences benefits 102,000 properties across Wales¹.

Why it matters for households

The warnings issued during Storm Isha are the same three-tier system used across Wales: Flood Alerts, Flood Warnings and Severe Flood Warnings, with the last meaning a danger to life¹. NRW's flood warnings for Wales are separate from the Environment Agency's service for England, and households can sign up for them free of charge through How to Sign Up for Free Flood Warnings. What each level means is set out in Flood Alerts, Flood Warnings and Severe Flood Warnings, and the Wales-specific warning and risk map arrangements are described in Wales: Natural Resources Wales Warnings and Risk Maps.

For households in areas that flooded, the report notes that Storm Isha followed a fortnight of cold and dry weather, which reduced the flood risk it posed¹. Roads were flooded in North Wales, and NRW records that the strong winds caused much disruption¹. The report does not give a count of properties flooded during Storm Isha, and no such figure has been reported.

The wider winter context matters for households in flood risk areas. NRW reports that October 2023 to March 2024 was the second wettest winter ever in the UK, according to the Met Office, with catchments saturated throughout and river levels sensitive to any rainfall¹. The report also cites Met Office analysis that there was 20% more rainfall, and that rainfall was 15% more intense, due to climate change¹. NRW's guidance for households preparing for flooding is covered in the flooding hub and the storms and snow hub, including the Checklist When a Flood Warning Is Issued, Flood Doors and Flood Windows and Home Insurance in a Flood Risk Area and Flood Re.

What happens next

NRW reports that it made significant progress on the development of a new and updated Flood Warning Service, which it says will enter operation in the summer¹. The report also records that it published its updated Flood Risk Management Plan in November 2023, setting out priorities for managing flood risk for the next six years, and that in January 2024 it published a report on the level of investment required in flood defences to manage Wales' future flood risk from rivers and the sea¹. NRW says it secured an additional £7m in October 2023¹.