Multi-Day Storm System Threatens Europe with Catastrophic Flooding
The European continent faces a dramatic weather transformation as the historic heat dome that dominated mid-August has collapsed, replaced by an aggressive low-pressure system tracking through the Alps. This multi-day severe weather outbreak poses significant flooding risks across northern Mediterranean regions, with particular concern for Italy and the western Balkans.
Current Weather Pattern Analysis
After weeks of record-breaking temperatures, a deep atmospheric trough has developed over central Europe, creating conditions for widespread severe weather. The Mediterranean Sea, warmed to unprecedented levels during the recent heatwave, now provides abundant moisture to fuel intense thunderstorm development.
Surface analysis indicates a shallow low-pressure system positioned over northern Italy, gradually tracking eastward toward the Adriatic Sea and Balkan Peninsula. While not exceptionally deep, this system maintains a strong pressure gradient supporting powerful moisture transport from the Mediterranean.
Recent Flooding Events Signal Greater Danger Ahead
Recent flooding footage from Italian cities demonstrates the destructive potential of flash floods in urban areas. Videos show torrential waters overwhelming streets, sweeping away vehicles, and transforming quiet neighborhoods into raging rivers. These events serve as a preview of potentially more severe conditions forecast for the coming days, with ECMWF models indicating even more intense precipitation rates.
Current Weather Warnings and Alerts
Based on Meteoalarm data, the following warning levels are currently in effect across Europe:
Extreme Risk Level (Red Warnings – Level 4)
Italy: Liguria, Tuscany, Emilia-Romagna, and Veneto regions face the highest threat level. Authorities recommend avoiding non-essential travel and preparing for potential evacuations in flood-prone areas.
Croatia: Istria Peninsula and Kvarner region, including the city of Rijeka, are under maximum alert status due to forecast extreme rainfall accumulations.
Slovenia: Coastal region and areas around Ljubljana face critical conditions with expected rainfall totals exceeding 150mm in 24-48 hours.
High Risk Level (Orange Warnings – Level 3)
Austria: Carinthia and Tyrol regions anticipate significant thunderstorm activity with potential for localized flooding and damaging winds.
Switzerland: Ticino and southern cantons expect heavy precipitation with possible impacts on transportation networks.
Bosnia and Herzegovina: Northwestern regions face elevated risk of severe weather with flooding potential.
Detailed Country and Capital City Forecasts
WEATHER FORECAST 21-23 AUGUST #Oslo #Stockholm #Helsinki #Tallinn #Riga #Vilnius #Warsaw #Chisinau #Glasgow #Dublin #London #Amsterdam #Berlin #Prague #Bratislava #Zurich #Vienna #Budapest #Belgrade #Sofia #Bucharest #Athens #Ankara #Paris #Rome #Madrid #Lisbon pic.twitter.com/r5WSmyLMQX
— City Weather (@ukcityweather) August 20, 2025
High Pressure Zones – Stable Conditions
Madrid, Spain Temperature range: 38-40°C Conditions: Dry and stable under anticyclonic influence Wind: Light westerly 10-15 km/h Precipitation: None expected
Lisbon, Portugal Temperature range: 36-39°C Conditions: Clear skies with possible late-day isolated thunderstorms Humidity: Moderate at 45-55%
Paris, France Temperature range: 32-35°C
Conditions: Variable cloud cover, generally dry Wind: Southwest 15-20 km/h
London, United Kingdom Temperature range: 26-29°C Conditions: Brief showers possible, otherwise partly cloudy Pressure: Rising to 1018 hPa
Berlin, Germany Temperature range: 28-31°C Conditions: Moderately warm with increasing cloud cover Wind: Variable, becoming southeasterly
Extreme Weather Zone – Critical Conditions
Rome, Italy Temperature range: 28-32°C (significant cooling trend) Precipitation: 150-250mm over 48 hours Wind: Gusts up to 100 km/h during thunderstorms Hazards: Hail up to 5cm diameter, flash flooding in urban areas Meteoalarm Status: Red level for entire central Italy region
The capital region faces particular vulnerability due to urbanization and limited drainage capacity. The Tiber River system requires close monitoring as upstream rainfall could cause rapid level increases.
Zagreb, Croatia Temperature range: 24-28°C Precipitation: 120-200mm expected Storm characteristics: Supercell development with tornado potential River levels: Sava River approaching flood stage Meteoalarm Status: Red level with evacuation recommendations for low-lying areas
Ljubljana, Slovenia Temperature range: 22-26°C
Precipitation: 100-180mm anticipated River concerns: Critical rise expected on Sava and Drava rivers Infrastructure: Potential disruption to rail and road networks Meteoalarm Status: Orange level with flood preparations underway
Vienna, Austria Temperature range: 24-28°C Precipitation: 60-100mm possible Wind: Sustained 40-50 km/h, gusts to 80 km/h Meteoalarm Status: Yellow level, monitoring conditions
Bern, Switzerland
Temperature range: 18-24°C (notable cooling) Mountain conditions: Snow above 2000m elevation Southern cantons: 80-120mm rainfall expected Alpine concerns: Rockfall and debris flow risk increased Meteoalarm Status: Orange for Ticino region
Moderate Conditions – Transitional Weather
Amsterdam, Netherlands Temperature: 24-27°C with variable cloud cover and brief shower potential
Brussels, Belgium Temperature: 25-28°C with possible afternoon thunderstorms
Luxembourg City Temperature: 26-29°C with localized storm development possible
Copenhagen, Denmark Temperature: 22-25°C, cooler than seasonal average
Eastern Europe – Weather Transition Zone
Warsaw, Poland Temperature: 26-30°C with thunderstorm and hail risk increasing
Prague, Czech Republic
Temperature: 24-28°C with intense rainfall periods expected
Bratislava, Slovakia Temperature: 25-29°C with flood risk along Danube tributaries
Budapest, Hungary Temperature: 28-32°C with supercell thunderstorm potential
ECMWF Model Analysis and Technical Forecast
Wednesday, August 21 Synoptic Pattern
The cyclonic center positions over northern Italy with central pressure around 995 hPa. An active frontal system extends from the Gulf of Genoa across the Adriatic Sea, supported by upper-level divergence in the left-exit region of a powerful jet streak.
Wind speeds at 200-300 hPa levels reach 200+ km/h, providing strong forcing for ascent. Convective Available Potential Energy (CAPE) values exceed 3000 J/kg across the region, indicating extreme atmospheric instability.
Sea surface temperatures in the Mediterranean remain 4-5°C above normal at 29-30°C, providing abundant moisture for storm development.
Thursday, August 22 Evolution
The surface low tracks eastward toward the Balkan Peninsula while maintaining intensity. The most significant severe weather threat shifts to the Adriatic Sea region and western Balkans.
Upper-level support remains strong with continued jet stream positioning favorable for organized storm development. Wind shear parameters support supercell thunderstorms with enhanced tornado potential over water.
Weekend Outlook
The system gradually weakens and moves eastward by Friday evening. A much cooler air mass follows, bringing temperatures 8-12°C below normal for late August across central and eastern Europe.
Record Weather Events from Previous Week
Temperature Records Achieved
Sicily recorded 48.2°C, establishing a new August maximum for the island. Sardinia reached 47.8°C while southern Spain measured 46.9°C in Córdoba. Portugal documented 46.1°C in Amareleja.
Wind Anomalies
Corsica experienced exceptional Mistral winds with gusts reaching 185 km/h, while the Balearic Islands recorded sustained winds of 165 km/h during a rare late-summer wind event.
Sea Temperature Records
The Mediterranean Sea averaged 29.8°C, representing a 4°C positive anomaly. The Adriatic Sea reached 28.5°C, setting a new August record for the basin.
Lightning Activity
France recorded 89,000 lightning strikes in a single day on August 15, while Germany documented 156,000 strikes, both representing daily records for their respective countries.
Safety Recommendations and Preparedness Measures
Public Safety Guidelines
Citizens in affected areas should avoid unnecessary travel during peak storm periods. Maintain emergency supplies including water and non-perishable food for 3-4 days. Monitor local river and stream levels, particularly in areas with known flood history.
Secure outdoor furniture and temporary structures against high winds. Keep mobile devices charged and maintain access to battery-powered weather radios for emergency communications.
Transportation Safety
Motorists must never attempt to cross flooded roadways, as water depth and current strength are difficult to assess. Avoid parking under trees during thunderstorms due to falling branch risk. Reduce driving speeds when visibility drops below 200 meters during heavy precipitation.
Aviation Impacts
Significant flight disruptions are anticipated at airports in Venice, Milan, Zagreb, and Ljubljana. Passengers should verify flight status before traveling to airports and expect possible multi-day delays.
Forecast Confidence and Updates
This forecast carries high confidence based on strong model agreement across multiple numerical weather prediction systems. The synoptic pattern is well-defined with clear physical mechanisms supporting the severe weather development.
Next detailed update scheduled for August 21, 12:00 UTC. Continuous monitoring of radar and satellite data will provide real-time situational awareness as conditions develop.
Weather conditions across Europe will be monitored continuously with updates provided as significant changes occur in the forecast scenario. Citizens are advised to stay informed through official meteorological services and local emergency management authorities.
Gleb Perov is the founder and chief meteorologist of POGODNIK, a leading weather forecasting service in Eastern Europe. With over 15 years of hands-on experience in meteorology and climate analysis, he has worked private weather services.
Gleb is the author of numerous scientific and analytical publications on climate, magnetic storms, and atmospheric processes. He regularly collaborates with major international agencies such as NOAA, ECMWF.
