March too mild, wet and cloudy so far

The final figures

Below are the final figures for the weather last March (see Figs. 1 to 3). Over the whole of Switzerland, March ended with a surplus of around 2.2 degrees in terms of temperatures, a surplus of just over 70% in terms of precipitation and a deficit of just under 30% in terms of sunshine duration. This means that the precipitation surplus has increased significantly since the provisional balance of March 28 due to large amounts of precipitation on the southern slopes of the Alps (from just over 60% to just over 70%). In some places in the south, it was the wettest March since measurements began (e.g. in Comprovasco, Cevio or Mosogno). In addition, the temperature surplus rose from 2 to 2.2 degrees due to above-average mild Easter weather in the north, making last March the 10th warmest March since records began in 1864. The deficit in sunshine duration also increased from just over 23% to over 28% due to the often cloudy weather of the last few days.

In addition, there have been some changes in the strongest winds since the provisional balance, with some stormy Föhn wind s at low altitudes and stormy southerly winds on the mountains. The strongest gusts were recorded at low altitudes in Altdorf with 130 km/h and on the mountains on the Gütsch above Andermatt with 190 km/h (second highest value at this station since measurements began) (see Figs. 4 and 5).

Finally, an overview of the deviations in temperature, precipitation and sunshine duration for some stations last March compared to the long-term average from 1991 to 2020.

The weather in March 2024

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Provisional March balance sheet

March was too mild, wet and cloudy for the whole of Switzerland. Below is a brief overview of the individual parameters.

Around 2 degrees too mild

March 2024 is in line with the last few months, most of which were significantly too mild; the last month that was too cool compared to the long-term average from 1991 to 2020 was April 2023! Across Switzerland, the excess temperature in March is around 2 degrees (see Fig. 1).

The temperature deviation is slightly greater in the north than in the south. The surplus is greatest in eastern Switzerland, at over 2.5 degrees in some places.

Only isolated frost

March brought only isolated frost on the Swiss Plateau and in the deep Alpine valleys (see Fig. 2). In Basel, Neuchâtel, Lausanne and Lugano, for example, the last frost day was still in January!

Vegetation development continues on record course

Due to the mostly above-average temperatures since mid-January, vegetation development is still far ahead of the long-term average, and the first apple trees will soon begin to blossom, more than 3 weeks earlier than normal (see Fig. 3). Frost would already be causing major damage to the fruit crops, but fortunately none is in sight for the time being.

The pollen season is also much further advanced than normal, with birch trees, which produce very allergenic pollen, already in bloom (see here).

Clearly too wet in the south, too dry in the west

Across Switzerland as a whole, March was clearly too wet, with a current surplus of just over 60% (see Fig. 4). However, the precipitation was very unevenly distributed across Switzerland. It was clearly too wet in the south in particular, but to a lesser extent also in central and eastern Switzerland, while it was too dry in many places in the west. In Geneva, only around half of the normal March precipitation has fallen so far.

By the end of the month, there will be a lot more precipitation in the south over the Easter period, so that the surplus will be even greater here (for the expected precipitation totals over the Easter period, see here).

Above-average amounts of snow at high altitudes

Compared to the long-term average, the amounts of snow at altitudes from around 2000 to 2500 meters are in some cases well above average, but clearly below average below that (see Figs. 5 and 6). This reflects the often above-average amounts of precipitation in recent months, albeit with a high snow line in many cases.

Too little sun

The sun shone less frequently than normal in March, with a deficit of just over 20% across Switzerland as a whole (see Fig. 7). The deviation is smallest in eastern Switzerland at locally less than 10%, while it is greatest in the central Alps at over 40% in places.

South foehn again and again

With the south to south-westerly winds that also occurred frequently in the second half of March, the northern Alpine valleys repeatedly experienced foehn winds. This occasionally blew through the valleys at gale force (see Fig. 8). From Good Friday tomorrow until Easter Sunday and thus until the end of the month, the northern Alpine valleys will once again experience stormy foehn winds (see here), with the foehn gusts likely to top the previous ones in many places.

 

Far too mild in the north

After the record mild February with a temperature deviation of 4.7 degrees across Switzerland (see February balance sheet here), the first half of March also shows a temperature surplus, although this is significantly lower at 1.5 degrees (see Fig. 1). The temperature surplus is greatest in the north-east, with over 2 degrees to almost 3 degrees in many places. In contrast, the surplus is less pronounced in Ticino and large parts of Valais, with temperatures well below 1 degree in some places.

A look at the maximum and minimum temperatures shows that the surplus of minimum temperatures of around 2 degrees is significantly greater than the surplus of maximum temperatures of around 1 degree. This means that mild nights were primarily responsible for the excess.

Isolated frost days in the lowlands

As in February, in the first half of March there were at most isolated frost days in the swiss plateau and in the lower Alpine valleys (minimums below 0 degrees, see Fig. 2). In Basel, Neuchâtel, Lausanne and Lugano, for example, the last frost day was in January!

Record advanced vegetation development

Vegetation development is currently more advanced than ever before, with a lead of around 3 weeks over the long-term norm at low altitudes (see here)! The current state of vegetation roughly corresponds to the first decade of April (see Fig. 3). This poses a number of risks, in particular any late frosts in April could cause major damage (see here).

Far too wet in the south, far too dry in the west

Across Switzerland, March has been too wet so far, with a surplus of around 63% (see Fig. 4). In the south in particular, there has been massively too much precipitation so far, with Mosogno showing the greatest deviation with an excess of 559%. Stabio, for example, already received around twice the normal precipitation for the whole of March. The large amount of precipitation was due to significant south-facing accumulations from March 1 to 3 and on March 9 and 10. While German-speaking Switzerland was also occasionally affected by somewhat heavier precipitation, resulting in a fairly widespread precipitation surplus, French-speaking Switzerland was spared heavy precipitation and it was far too dry here. At 90%, the deficit is greatest in Bière, where there has only been around 3 mm of precipitation so far in March.

Short winter greetings at low altitudes

In terms of the air mass, it would never have snowed down to low altitudes in March. However, when there was heavy precipitation, the effect of so-called precipitation cooling kicked in, resulting in isolated snowfall down to low altitudes. For example, it turned white in large parts of central Switzerland on March 6 (see Fig. 5), and wet flakes fell in the Chur Rhine Valley on March 13.

Widespread overcast

March has been too cloudy across the board so far, with a 36.5% deficit in sunshine duration over the whole of Switzerland. There was particularly little sunshine in the central and western Central Plateau, while the deficit was lowest in the eastern foothills of the Alps, northern Grisons and central and lower Valais (see Fig. 6).

Frequent southerly foehn

With the south to south-westerly winds that have frequently occurred so far in March, the northern Alpine valleys have repeatedly experienced Foehn winds. This occasionally blew through the valleys at gale force. The strongest Foehn gusts were recorded in Adelboden at 127 km/h, followed by Altenrhein at 114 km/h and Meiringen at 109 km/h (see Fig. 7). There were occasional even stronger gusts on the mountains, with a Foehn gust of 189 km/h recorded on the Gütsch/Gotthard on March 9 (although this does not appear in the top 10 of the strongest gusts ever measured here).