Switzerland braces for more heatwaves, droughts and violent storms

Skiers in Engelberg on January 7, 2023. The so-called zero-degree limit, where rain turns to snow, has risen by several hundred metres since the early 20th century and is projected to climb another 550 metres by the end of the century, to around 1,450 metres in winter. Keystone / Urs Flueeler

Switzerland is heading for a future that is hotter, drier and more unpredictable, with less snow and heavier rainfall, according to national climate projections released by the country’s leading scientific institutions.

The studyExternal link, unveiled on Tuesday by the Federal Office of Meteorology and Climatology (MeteoSwiss) and the federal technology institute ETH Zurich, paints a stark picture of what lies ahead for the Alpine nation, which is warming almost twice as fast as the global average.

Warming at double speed

Global temperatures have already risen by about 1.3–1.4°C since pre-industrial times. In Switzerland, that figure has reached 2.9°C, according to 2024 data.

If global heating continues unchecked to 3°C, the researchers say, the country could face warming of 4.9°C – a scenario they warn could unfold as early as 2065 if emissions do not fall sharply.

A surge in heat extremes

Among the four main far-reaching consequences, the report foresees a rise in heatwaves and tropical nights, particularly in urban areas such as Lugano, Zurich, Geneva and Basel.

In a 3°C warmer world, the hottest summer day in Basel could hit 38.8°C, up from 34.4°C in the 1991–2020 reference period. Days of extreme heat that currently occur once every 50 years could become up to 17 times more frequent. The city of Zurich is expected to experience approximately five times more tropical nights per year, on average.

Expected change in the number of days per year with temperatures of at least 30°C. Shown are the mean values measured in the reference period 1991–2020 and the possible range in a 3°C world. Swiss Federal Office of Meteorology and Climatology MeteoSwiss, ETH Zurich,

Lowland regions and urban areas are expected to suffer the greatest heat stress, but even high-altitude valleys and Alpine foothills could see prolonged heat events that were once rare.

Summers drying out

While winters may bring more rain, the country’s summers will grow markedly drier, scientists warn.

Rising temperatures, increased evaporation and declining summer rainfall are expected to leave Swiss soils parched. Summer droughts have already increased over the past four decades. A drought that previously occurred once a decade could strike three times as often, with a 44% increase in intensity. The risk of forest fires is also likely to climb sharply.

Number of days per year with a high weather-related forest fire risk in Sion. The expected value (median of all simulations) and the possible range (spread of the simulations) are indicated. Swiss Federal Office of Meteorology and Climatology MeteoSwiss, ETH Zurich,

Rainfall turning violent

Switzerland must nonetheless expect an increase in heavy rains across all seasons, say the experts. As temperatures rise, both the intensity and frequency of heavy downpours, especially short, intense storms, will increase.

Such events could become up to 30% more intense, with rainfall increasingly concentrated into shorter periods – a shift that raises the danger of flash floods, mudslides and landslides.

Change in average precipitation and extreme precipitation in Switzerland. Swiss Federal Office of Meteorology and Climatology MeteoSwiss, ETH Zurich,

Snow retreating to higher ground

The snowline in the Swiss Alps is retreating fast. The so-called zero-degree limit, where rain turns to snow, has risen by several hundred metres since the early 20th century and is projected to climb another 550 metres by the end of the century, to around 1,450 metres in winter.

That means more winter rain and less snow. In a 3°C world, the share of snowfall would drop by about 25%, while rainfall would almost double. Natural snow cover at lower altitudes could vanish almost entirely, with profound consequences for ski tourism.

Average elevation of the zero-degree line in winter (below) and summer (above) for mountains in Swiss Alps.. The expected value (median of all simulations) and the possible range (spread of the simulations) are indicated. Swiss Federal Office of Meteorology and Climatology MeteoSwiss, ETH Zurich,

‘Mitigation still matters’

“With ambitious climate change mitigation and global net-zero emissions by 2050, most of the future long-term warming and therefore many of the resulting further impacts could be averted,” said ETH Zurich climate researcher Reto Knutti.

Switzerland ratified the Paris Agreement in 2017 and has pledged to cut greenhouse gas emissions by half by 2030 and reach net zero by 2050.

For its latest intermediary targets, the government announced in January that by 2035 the country should reduce its greenhouse gas emissions by at least 65% compared to 1990 levels, and by 59% on average between 2031 and 2035.

But the report’s authors caution that even with deep cuts, some further warming is inevitable – and societies must adapt.

“Global warming can at best be limited, but not reversed,” the authors said.

Commissioned by the Swiss government, the 2025 climate scenarios were developed by MeteoSwiss, ETH Zurich and the Center for Climate Systems Modeling (C2SM), with input from the University of Bern’s Oeschger Centre for Climate Change Research (OCCR) and the University of Lausanne, under the umbrella of the National Centre for Climate Services (NCCS).

They update earlier projections from 2007, 2011 and 2018, offering the most detailed vision yet of Switzerland’s climatic future. The key trends identified in CH2018 remain unchanged (continued warming, more frequent and intense heat extremes, heavier precipitation events, drier summers and winters with less snow), but with higher projected warming. In 2018, for example, scientists had predicted that the average temperature would be 2.5-4.5°C degrees higher than today. Droughts of about three weeks in summer were expected.

“The new climate scenarios give us a clearer picture of changes in Switzerland’s climate in the decades ahead. They help us to assess developments and to plan appropriate measures, with a view to protecting our environment, cities and agriculture,” said Interior Minister Elisabeth Baume-Schneider.

Edited by Virginie Mangin/ts