Residents in parts of Murcia have been urged to remain indoors or seek shelter on higher ground after a red alert was issued by state weather agency Aemet.
The highest possible warning was activated in Campo de Cartagena and Mazarron from 2pm until 6pm on Friday. It will then fall back to orange until midnight.
An ES-Alert emergency message was sent to mobile phones, warning people to avoid travelling on foot or by car unless absolutely necessary.
People were told not to cross flooded roads, dry riverbeds, watercourses or fords and to call 112 only in a genuine emergency.
The regional authorities activated Level 1 of the Inunmur flood emergency plan as heavy downpours caused flooding and disruption across the south-east of Spain.
Schools closed
School was suspended in Cartagena, Mazarron, Fuente Alamo, La Union, Torre Pacheco, San Javier, Los Alcazares and San Pedro del Pinatar.
Early-intervention centres were also closed in those municipalities to prevent families and staff from having to travel.
Cartagena council opened community centres in Pozo Estrecho and La Palma to assist anyone affected by the severe weather.
Sporting activities inside municipal facilities were suspended alongside cultural and educational events, with sports halls placed at the disposal of the emergency operation.
Emergency alert across Murcia
The remainder of the Murcia region was placed under an orange warning for rain and thunderstorms.
Aemet forecast rainfall of up to 40 litres per square metre in one hour in the Guadalentin Valley, Lorca, Aguilas and the Vega del Segura.
Orange warnings were also activated for the Altiplano and north-western districts from 2pm until midnight.
Regional president Fernando Lopez Miras urged residents to act cautiously, avoid unnecessary risks and follow information from official sources.
Government delegate Francisco Lucas also warned people to stay away from flood channels and low-lying areas as storms developed across the southern half of the region.
Rain to continue
Unsettled conditions are expected to continue on Saturday, when Aemet has issued a yellow warning for storms and rainfall of up to 15 litres per square metre in one hour in north-western Murcia.
Rain and possible thunderstorms are forecast across Murcia city, Cartagena, Lorca, Caravaca de la Cruz, Jumilla and Aguilas.
Conditions should improve partially on Sunday, particularly along the coast and in central parts of the region.
However, further heavy showers and thunderstorms may develop inland later in the day, with the probability of rain reaching 95% around Caravaca de la Cruz and 80% in Jumilla.
