Thunderstorms over the Sottoceneri, but the heat warning runs to 15 August

MeteoSwiss issued a level 3 thunderstorm warning for the whole of the Sottoceneri. The alert was valid until 10.10 am on Friday 7 August.

These are the first thunderstorms after days of intense heat. The weather service describes them as a brief respite from the oppressive conditions of recent weeks.

The respite does not change the wider picture. The heatwave warning for Ticino has been extended until 15 August, meaning at least another week.

One level down, not a change of season

From 8 pm on Friday the heatwave warning drops to level 3. The weekend is expected to bring a slight fall in maximum temperatures.

The forecast for Friday gave values between 22 and 33 degrees. That is a limited decline, and it does not interrupt the ongoing heatwave.

Dropping to a lower level does not cancel the measures. The warning stays active and MeteoSwiss continues to flag the risk linked to high temperatures.

The two phenomena last different lengths of time. Thunderstorms are an episode of a few hours, while the heatwave warning covers more than a week and applies across the whole area.

Summer thunderstorms in Ticino tend to be intense and localised. They bring rainfall concentrated into a short time, which dry ground struggles to absorb.

That is precisely the issue where drought is concerned. Several municipalities in the canton have asked residents to cut their use of drinking water, and drought level 1 has been declared in the Lower Mendrisiotto.

A few hours of unsettled weather is not enough to rebuild water reserves. What would be needed is rainfall spread over several days, which the forecasts do not currently show.

For people who work outdoors and for those most exposed to heat, the situation therefore remains unchanged. The recommendations linked to the heatwave warning stay in force until 15 August.