Weather alert for Southern Italy: risk of cloudbursts and flash floods.

A level 1 weather alert has been issued for Southern Italy and the central Mediterranean basin for Sunday, September 20, 2026. Meteorologists forecast a high risk of torrential downpours and flash floods, fueled by a particularly humid and unstable air mass. Persistent convective phenomena could cause flash floods, primarily due to the slow movement of thunderstorm cells that would dump repeated rainfall on the same areas.

The alert, based on data from the European organization Estofex, indicates precipitable water (TPW) values between 30 and 40 millimeters, up to 150% higher than the reference climatology. The focus is on the central-southern Mediterranean, with possible repercussions also on the Strait of Sicily should a depression vortex form over Tunisia. The main risk concerns urban drainage systems, which could become inefficient within minutes.

Today's alert stems from a specific atmospheric configuration affecting the Mediterranean basin. The incoming meteorological phenomenon is classified as "flash flooding," which differs from persistent rainfall because it is characterized by extremely concentrated precipitation over very short periods. This type of event occurs when a mass of moisture-rich air encounters unstable conditions, generating violent thunderstorms that discharge large amounts of water over restricted areas.

The current situation is monitored through the TPW (Total Precipitable Water) parameter, which measures all the water present in a column of air from top to bottom. Current values, up to 150% above the seasonal average, indicate an exceptional availability of "fuel" for thunderstorms. The European organization Estofex, specialized in severe thunderstorm forecasts, issues these bulletins when conditions become potentially dangerous. The particular concern for Sunday arises from the combination of high humidity and the predicted slow movement of thunderstorm cells, which would increase localized accumulations.