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Hydrology Summary Bulletin – May 2026

Hydrology bulletin on rainfall, river flows, lake levels, groundwater levels and spring outflows for May 2026.

May 2026 was mild overall. A relatively cool first two thirds was followed by a very warm final third.
It was dry in most places, especially in the East. The early part of the month was influenced by low
pressure and Arctic air from the north, bringing cooler temperatures and occasional rain or
showers. Mid-month, Atlantic low pressure introduced milder conditions with more widespread
rainfall. In the final week, strong high pressure and a hot continental airmass led to unusually high
temperatures, particularly between 25th–27th May. Thunderstorms occurred late in the month,
followed by a return to cooler Atlantic conditions with mixed rain and dry periods.
Compared to April 2026, average river flows in May decreased across all 135 river monitoring
stations assessed, with the greatest decreases observed in the east. Overall, 44% of the monthly
average river flows were below the normal long-term range, particularly in the east and southeast.
Although lake levels decreased at all monitored sites, 42% remained above the long-term normal
range. Similarly, groundwater levels decreased at all 30 monitoring locations, yet 40% remained
above the long-term normal range. Of the four spring flows monitored, 2 were classified as ‘above
normal’ and 2 were within the ‘normal’ range.

Download and read the full Hydrology bulletin for May 2026 here.

About EPA Monthly Hydrology Bulletin: Monthly Hydrology Bulletin – Catchments.ie – Catchments.ie

Access previous EPA monthly Hydrology Bulletins here: Monitoring & Assessment: Freshwater & Marine Publications | Environmental Protection Agency

About author

EPA Catchments Unit

Administrator

The EPA Catchments Unit is based in Dublin, and the team is involved with catchment science, chemistry, ecology, hydromorphology, modelling, Geographic Information Systems and planning. We work with the wider EPA, all of our local authorities, the Local Authority Waters and Communities Office, the Department of Housing, Planning and Local Government, and other public bodies and Departments to ensure we have the best available data and information about our catchments.

Who is involved?
Quite simply, everyone in Ireland has a role to play. This can be from something as simple as making sure you don’t pollute your local stream, or a local community working together to establish a Rivers Trust to enhance the rivers and lakes in their area, to a Government Department or Agency helping a Minister implement a new policy to help protect and enhance all our water bodies.

This website has been developed and is maintained by the Environmental Protection Agency, and is a collaboration between the Department of Housing, Planning and Local Government, the Environmental Protection Agency, and the Local Authority Waters Programme.

Local Authority Waters Programme

The Local Authority Waters Programme coordinates the efforts of local authorities and other public bodies in the implementation of the River Basin Management Plan, and supports local community and stakeholder involvement in managing our natural waters, for everyone’s benefit.

Environmental Protection Agency

The EPA is responsible for coordinating the monitoring, assessment and reporting on the status of our 4,842 water bodies, looking at trends and changes, determining which waterbodies are at risk and what could be causing this, and drafting environmental objectives for each.

Department of Housing, Local Government and Heritage

The Department is responsible for making sure that the right policies, regulations and resources are in place to implement the Water Framework Directive, and developing a River Basin Management Plan and Programme of Measures to protect and restore our waters.