Thunderstorm activity is identified by monitoring the radio signals created by electrical storms. The resulting information, called Fferic Reports, is filed to Met Eireann.
The location of the electrical storms can then be calculated by triangulation. Ninety five per cent of electrical storm activity takes place between clouds.
The following is a sample of some of the reports, which were filed on the hour from midnight on Sunday:
Midnight: Valencia, Leixlip, Waterford, Enniscorthy.
1.00 a.m.: Killarney, Enniscorthy, Bray, Baltinglass, Dublin Airport, Dublin Bay, North Kildare, Offaly, Athlone, Glenbeigh.
2.00 a.m.: Glenbeigh, Killarney, Loop Head, Macroom, Tullamore, Portlaoise, Athlone, Kinnegad, Dundalk.
3.00 a.m.: Killarney, Loop Head, Rathkeale, Kilkee, Lahinch, Birr, Enniscorthy, Carrick-onShannon, Cavan, Monaghan, Fermanagh.
4.00 a.m.: Fermanagh, Ballykelly, Derry, Armagh, Lurgan, Carrick-on Shannon, South Donegal, Dungannon, North Antrim.
5.00 a.m.: Clifden, Roscommon.
6.00 a.m.: no reports.