Unstable weather for Sunday, September 20th, with thunderstorms in the South and Sicily.

Sunday, September 20, 2026, will be a day of unsettled weather for several regions of central and southern Italy. While the North and the mid-to-upper Tyrrhenian coast will enjoy largely sunny weather thanks to strengthening high pressure, the South and the islands will have to contend with showers and thunderstorms, in some cases even heavy ones.

The most affected areas will be Calabria, Sicily, central-southern Campania, and Basilicata, especially in inland areas. The morning will see showers over the Ionian sectors of Calabria and the eastern coasts of central-southern Sardinia. In the afternoon, the instability will intensify with widespread thunderstorms over central-eastern Sicily, inland and Tyrrhenian Calabria, and some inland areas of Campania and Basilicata. Temperatures will drop in the South and rise elsewhere.

The weather situation on Sunday, September 20th, is the final chapter of a period of instability that has affected the central Mediterranean. In the preceding days, the passage of a 'northern unstable trough'—a low-pressure area—brought widespread showers and thunderstorms to several Italian regions. This disturbed system is now retreating, pushed eastward by the gradual strengthening of an anticyclone (high pressure) arriving from France and Western Europe.

However, the stabilization process is not uniform. While the North and the central-northern Tyrrhenian Sea are already under the influence of high pressure, the South and the islands remain, at least for Sunday, under the residual influence of the unstable circulation. In particular, a 'weak cyclonic curvature' (a remnant of low pressure) at higher altitudes maintains moderately unstable northwesterly flows over Calabria, Sicily, and parts of the southern peninsula, triggering afternoon thunderstorms. This is a typical seasonal transition situation, where different air masses clash, leading to variable weather.