Storm Alice in Spain 2025: Floods and How to Prevent Mould

Storm “Alice”: Heavy rain and flooding in Spain

In mid‑October 2025, the Mediterranean weather system “Alice” hit several regions of Spain with full force. The storm brought enormous amounts of rain that caused flooding and landslides in a matter of hours. Catalonia, the Valencia region and the Balearic Islands were particularly hard hit.

Severe weather in Catalonia and Valencia

By 13 October, news reports explained that Spain’s meteorological agency AEMET had issued the highest weather alert for parts of Catalonia and Valencia. In Tarragona province, torrential rain turned towns such as La Ràpita and Santa Bàrbara into lakes within a few hours. Cars stalled in the rising water and people had to be rescued from their vehicles .

The deluge forced the railway to suspend services between Barcelona and Valencia; roads became impassable and many rural routes were closed . AEMET warned of further downpours and estimated that up to 180 millimetres of rain could fall .

Flooding in the Balearic Islands

The Balearics were not spared. On Ibiza, parts of the EI‑20 motorway were under water and two people had to be rescued from their stranded car . The Balearic emergency services logged 38 floods on Ibiza and eight on Mallorca . In Palma and other towns the water poured into car parks, flooded shops and cellars and dozens of flights were cancelled or delayed . Weather warnings remained in place until Tuesday.

Cause: A DANA – isolated upper‑level low over the Mediterranean

Meteorologists explained that “Alice” was triggered by a so‑called DANA (a Spanish acronym for an isolated upper‑level low). In such events, a cold pocket of air descends from the jet stream onto the warm Mediterranean, producing extreme thunderstorms that can dump huge amounts of rain locally. According to the Frankfurter Rundschau, these DANA events are rare but can bring more than 300 litres of rain per square metre in just a few hours and cause catastrophic flooding .

After the flood: Why quick action matters

In addition to the obvious damage caused by water, floods harbour a less visible risk: mould. Once moisture has seeped into walls, floors and furniture, fungal spores can start growing within 24 to 36 hours . Rooms contaminated with mould endanger health — especially for people with asthma, allergies or weakened immune systems .

To ensure that water damage does not turn into a long‑term mould problem, the first few hours are critical. Consumer advice centres point out that moisture often penetrates deep into insulation materials and wooden structures and remains trapped there. If it is not removed quickly, musty odours and mould growth can appear after just a few days .

Immediate steps after a flood

The following actions will help prevent mould and additional damage:

1. Enter safely. Before you go inside, make sure the electricity and gas are switched off. Check the structural integrity of the house; if walls or ceilings are damaged, consult professionals.

2. Act quickly. Mould begins to grow within 24–36 hours . Remove standing water quickly using pumps or buckets and start clearing up immediately.

3. Ventilate thoroughly. According to the consumer association, shock ventilation (opening windows wide for a short period) is the first step once water has been pumped out and rooms cleared . Open all windows and doors to let air circulate. Be careful: uncontrolled draughts can spread smoke and spores; controlled cross‑ventilation through several windows is ideal.

4. Use technical drying equipment. Moisture often penetrates so deeply into masonry that natural drying is insufficient. Experts recommend starting technical drying quickly and monitoring progress with moisture measurements . Condensation dryers and turbo fans accelerate drying; for large‑scale damage, specialised companies should be hired .

5. Wear protective gear. During clean‑up, N95 or FFP2 masks, rubber gloves and protective goggles are essential. The CDC advises people with allergies, asthma or weakened immune systems to avoid clean‑up work .

6. Discard contaminated materials. Remove heavily soaked carpets, upholstered furniture, drywall and insulation. IQAir notes that porous materials should be disposed of because mould spores penetrate deeply and are difficult to remove .

7. Clean and disinfect. To combat mould, IQAir recommends a solution of 1.5 cups of household bleach per 1 gallon (3.8 L) of water . Scrub surfaces with this solution and rinse afterwards; never mix bleach and ammonia, as this produces toxic fumes.

8. Wash damp textiles. Clothing, curtains and other washable fabrics should be cleaned with hot water and detergent and then thoroughly dried.

9. Control indoor humidity. After drying, it is important to keep relative humidity between 35 and 50 percent. This reduces the risk of mould growth and improves indoor comfort . Hygrometers measure moisture levels; dehumidifiers help regulate them.

10. Use air purifiers. High‑quality air cleaners with HEPA or electrostatic filters can reduce airborne spores during restoration work .

11. Call in professionals for major damage. If sewage has entered the house or mould covers a large area, hire a specialised company. Ensure that the firm has experience in mould remediation and follows current guidelines .

    
    

Special considerations when drying buildings

Drying walls and floors is complex. Masonry or concrete walls can be dried fairly well after a structural inspection, whereas saturated gypsum board and insulation materials must be completely removed . Condensation dryers extract moisture from the indoor air and turbo fans ensure rapid air circulation . In many modern houses, vapour barriers prevent moisture from escaping; therefore it may be necessary to remove insulation from cavities or to use films as “air cushions” .

For interior plaster, remember that gypsum plaster becomes microbiologically contaminated after a short time and must be replaced . Mineral plasters based on cement or lime are more resistant to moisture . Exterior walls often take weeks to dry; a renovation plaster can help transport moisture outward and reduce salt efflorescence .

Long‑term protection and prevention

Even after restoration, there is work to be done. Repair leaky roofs, broken pipes and non‑waterproof basement windows to keep water out during the next heavy rain. Regular ventilation and proper heating help control indoor moisture. Open windows daily for a few minutes and keep living spaces at least 16 °C to prevent condensation. In areas prone to flooding, consider installing backflow valves in wastewater pipes and pressure‑resistant basement windows. Store important documents and valuables on upper floors. Many municipalities now offer information and advice on private flood preparedness.