Large parts of Wales could be hit by sudden flooding on Sunday night, warns weather department.
Torrential rain and thunderstorms could bring as much as 30mm to 40mm downpour is several places in an hour.
Met Office has issued a yellow warning for the southern parts of Wales and some places in mid Wales too from Sunday midnight to Monday evening, until 4 p.m.
Even though many areas would not be hit by such rains or to remain dry, but in some places the downpours could result with sudden flooding of roads.
Possible lightning is also in warning notice that may disrupt power.
The Met Office chief forecaster’s assessment also warns of frequent lightning, heavy rain, hail and gusty winds on Sunday evening.
The minimum temperature at night could reach as low as 12 degree C and during the day time the maximum temperature could be 21 degree C.
The thundery showers will start clearing northwards Monday morning, but humidity will remain in large parts of the region.
The Met Office adds rest of the week will remain mainly dry and odd shower will be seen on Tuesday or Wednesday.
The local authorities which are covered by the Met Office weather warning are Blaenau Gwent, Bridgend, Caerphilly, Cardiff, Merthyr Tydfil, Monmouthshire, Newport, Rhondda Cynon Taff, Torfaen, the Vale of Glamorgan, Carmarthenshire, Ceredigion, Neath Port Talbot, Pembrokeshire, Powys, and Swansea.
Travelers are alerted to take precautionary measures before movie out of home or hotel room and start ahead of scheduled time to reach the destination on time.