Hot: a weekend of 40 degrees with an African high-pressure system

The African high-pressure system is keeping Italia in the grip of oppressive heat, with temperatures relentlessly hovering around 39–40°C; however, it is already showing the first signs of weakening at its northernmost edge, giving way to Atlantic currents. This is highlighted by iLMeteo.it, which sees this as the prelude to a violent shift from the heatwave to thunderstorms. In 70% of cases, following such extreme heat, equally violent thunderstorms do indeed follow and, having struck Scotland, England, France and Spain, it is now Italia’s turn.

The figures coming in from abroad are staggering: 6,000 lightning strikes per hour were recorded across England and Scotland, a situation without precedent at those latitudes. The so-called ‘heat dome’ will begin to weaken from Monday 29 June across northern Italia, allowing the first intense weather events to form close to the Alps. From Tuesday 30th, the breakdown will be more pronounced and we can expect some showers that could extend as far as the Po Valley, releasing a very high amount of thermal energy.

On Wednesday 1 July, a low-pressure system, laden with cold air at high altitude, will move from Germany towards Italia. The impact could be very severe: heavy rain is forecast initially in the north (with a real risk of hailstorms and violent gusts of wind), before moving southwards towards central and southern Italy, where the disturbance will form a full-blown cyclone over the southern Tyrrhenian Sea by Thursday. Under the influence of this storm system, temperatures will drop sharply, although a subsequent, temporary return of high pressure cannot be entirely ruled out.

Looking a little further ahead, over the 10-day period for which there are no definitive forecasts, the weekend of 4–5 July could bring some interesting developments. The models suggest that the long-absent Azores High may return to Western Europe. For Italia, this would mean the arrival of northerly winds: a somewhat unsettled spell, with sunny mornings and a few more afternoon thunderstorms over the Alps and central and southern Italy, but in a much cooler and, at last, more bearable atmosphere.

Before we can look forward to some relief in July, however, we must get through the next few, extremely challenging hours, as this looks set to be the hottest weekend of the year. The peak of the high-pressure system: ‘unbearable’ heat, potentially harmful to health, will persist uninterrupted until Tuesday, with temperatures consistently reaching 40°C. The mid-week transition: it will be vital to monitor the intensity and spread of the thunderstorms on 1 July, as the clash between the existing extreme heat and the incoming cold air risks triggering particularly violent weather events.