The yellow warning covers 16 of Wales’ 22 council areas – Blaenau Gwent, Caerphilly, Carmarthenshire, Ceredigion, Conwy, Denbighshire, Flintshire, Gwynedd, Merthyr Tydfil, Monmouthshire, Neath Port Talbot, Powys, Rhondda Cynon Taf, Swansea, Torfaen and Wrexham.