Heavy rain will hit Strandzha and the southern Black Sea coast over the next 24 hours, Meteo Bulgaria says, citing the regional Swiss HD model.
Parts of the hills in Burgas province, mostly near the Turkish border, will get 50 to 70 litres of rain per square metre tomorrow. Over tomorrow and Friday, Malko Tarnovo and Tsarevo could see up to 150 litres per square metre.
Forecasters are telling people and local authorities in Burgas province to take care on Thursday and Friday, when land and sky will "merge" under the sheer amount of water.
Meteo Bulgaria says warm sea water is driving the first big spell of coastal rain this season. Neighbouring countries will get rain too.