Weather and climate in Sion (Switzerland)

The climate of Sion is moderately continental, with cold winters and warm summers.
The city is located in the south-west of Switzerland, in the canton of Valais, at 490 meters (1,600 feet), in a valley oriented from west to east, where rainfall is scarcer than in the rest of Switzerland. Furthermore, the amount of sunshine is comparable to that of the Canton of Ticino. A short distance away we find the ski resort of Crans-Montana, which is located at 1,500 meters (4,900 feet) above sea level.
The winter is cold. Cold air tends to stagnate in the valley, and at night, the temperature often drops below freezing, but during the day, the sun is seen a little more often than in the cities of the Swiss plateau such as Bern or Zurich. There may be relatively mild periods, when Atlantic currents prevail, and other colder periods, when the temperature drops below freezing. On average, 44 cm (17 in) of snow fall per year.
Sometimes, there can be cold spells, in which temperatures can drop as low as -10 °C (14 °F) or even below. The coldest record is -21 °C (-6 °F) and was set in January 1968 and in January 1979.
In summer, the temperatures are generally pleasant and lend themselves to outdoor activities, although sometimes there can be rains and thunderstorms.
At times, hot periods can occur, generally of short duration, which in recent years are becoming more frequent due to global warming, and in which the temperature can exceed 32 °C (90 °F). The highest record is 38 °C (100.4 °F) and was set in July 2015 and in July 2019. In 2022, the temperature reached 37 °C (98.6 °F) in June, 36.3 °C (97.3 °F) in July and 36.2 °C (97.2 °F) in August.

Best Time

The best time to visit Sion is from mid-May to mid-September, since it is the warmest and sunniest of the year. However, we cannot exclude some rain, or a bit of cool weather, or even cold, especially in May and early June.

Sion - Climate data

The average temperature of the coldest month (January) is of 1.0 °C (33.8 °F), that of the warmest month (July) is of 20.9 °C (69.6 °F). Here are the average temperatures.
Precipitation amounts to 585 millimeters (23 inches) per year: so, it is at an intermediate level. It ranges from 35 mm (1.4 in) in the driest months (March, April) to 70 mm (2.8 in) in the wettest one (December). Here is the average precipitation.
There are on average around 2135 sunshine hours per year. Here are the average hours of sunshine per day.

Sion - Weather by month

Based on the period 1991-2020

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January, the coldest month of the year, is generally a cold month. The average temperature is of 1.0 °C (34 °F), with a minimum of -3.1 °C (26.5 °F) and a maximum of 5.1 °C (41.2 °F).
On the coldest nights of the month, the temperature usually drops to around -9 °C (16 °F). However, it dropped to -16 °C (3.2 °F) in January 2005.
On the warmest days of the month, the temperature usually reaches around 11 °C (52 °F). However, it reached 16.8 °C (62.2 °F) in January 2007.
Precipitation amounts to 50 mm (2 in), distributed over 7 days.
The day lasts on average 9 hours and 5 minutes.
There are on average 3 hours of sunshine per day. So, the sun shines 32% of the time.
The average humidity is 77%. Hence, the air is normally humid.
The average wind speed is 6 kph (4 mph).

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February is generally a cold month. The average temperature is of 2.9 °C (37 °F), with a minimum of -2 °C (28.4 °F) and a maximum of 7.9 °C (46.1 °F).
On the coldest nights of the month, the temperature usually drops to around -7.5 °C (19 °F). However, it dropped to -15.9 °C (3.4 °F) in February 1999.
On the warmest days of the month, the temperature usually reaches around 15 °C (59.5 °F). However, it reached 21 °C (69.8 °F) in February 2017.
Precipitation amounts to 40 mm (1.6 in), distributed over 6 days.
The day lasts on average 10 hours and 25 minutes.
There are on average 4.5 hours of sunshine per day. So, the sun shines 44% of the time.
The average humidity is 69%.
The average wind speed is 7 kph (4 mph).

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March is generally a quite mild month. The average temperature is of 7.7 °C (46 °F), with a minimum of 1.7 °C (35.1 °F) and a maximum of 13.7 °C (56.7 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around -3.5 °C (26 °F). However, it dropped to -9.8 °C (14.4 °F) in March 2005.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 21 °C (70 °F). However, it reached 24.9 °C (76.8 °F) in March 2004.
Precipitation amounts to 35 mm (1.4 in), distributed over 6 days.
The day lasts on average 12 hours and 0 minutes.
There are on average 6 hours of sunshine per day. So, the sun shines 51% of the time.
The average humidity is 60%.
The average wind speed is 9 kph (5 mph).

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April is generally a mild month. The average temperature is of 11.4 °C (53 °F), with a minimum of 5.1 °C (41.2 °F) and a maximum of 17.8 °C (64 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 0 °C (31.5 °F). However, it dropped to -2 °C (28.4 °F) in April 2003.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 25 °C (77 °F). However, it reached 29 °C (84.2 °F) in April 2018.
Precipitation amounts to 35 mm (1.4 in), distributed over 5 days.
The day lasts on average 13 hours and 35 minutes.
There are on average 7 hours of sunshine per day. So, the sun shines 51% of the time.
The average humidity is 56%.
The average wind speed is 10 kph (6 mph).

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May is generally a very mild month. The average temperature is of 15.5 °C (60 °F), with a minimum of 9.2 °C (48.6 °F) and a maximum of 21.8 °C (71.3 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 4 °C (39 °F). However, it dropped to -0.4 °C (31.3 °F) in May 1991.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 29.5 °C (85 °F). However, it reached 35.1 °C (95.2 °F) in May 2009.
Precipitation amounts to 50 mm (2 in), distributed over 8 days.
The day lasts on average 15 hours and 0 minutes. So the days are long.
There are on average 7 hours of sunshine per day. So, the sun shines 48% of the time.
The average humidity is 60%.
The average wind speed is 10 kph (6 mph).

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June is generally a warm month. The average temperature is of 19.2 °C (67 °F), with a minimum of 12.8 °C (55.1 °F) and a maximum of 25.5 °C (78 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 7.5 °C (45 °F). However, it dropped to 1.5 °C (34.7 °F) in June 2006.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 32.5 °C (91 °F). However, it reached 36.7 °C (98.1 °F) in June 2019.
Precipitation amounts to 50 mm (2 in), distributed over 7 days.
The day lasts on average 15 hours and 40 minutes. So the days are long. June 21, the summer solstice, is the longest day of the year in the Northern Hemisphere.
There are on average 8.5 hours of sunshine per day. So, the sun shines 54% of the time.
The average humidity is 60%.
The average wind speed is 10 kph (6 mph).

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July, the warmest month of the year, is generally a warm month. The average temperature is of 20.9 °C (70 °F), with a minimum of 14.4 °C (58 °F) and a maximum of 27.3 °C (81.2 °F).
On the coldest nights of the month, the temperature usually drops to around 9.5 °C (49 °F). However, it dropped to 6.6 °C (43.9 °F) in July 1996.
On the warmest days of the month, the temperature usually reaches around 34 °C (93 °F). However, it reached 38 °C (100.4 °F) in July 2015.
Precipitation amounts to 65 mm (2.6 in), distributed over 8 days.
The day lasts on average 15 hours and 20 minutes. So the days are long.
There are on average 8.5 hours of sunshine per day. So, the sun shines 56% of the time.
The average humidity is 61%.
The average wind speed is 10 kph (6 mph).

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August is generally a warm month. The average temperature is of 20.3 °C (68 °F), with a minimum of 14 °C (57.3 °F) and a maximum of 26.5 °C (79.7 °F).
On the coldest nights of the month, the temperature usually drops to around 8.5 °C (47.5 °F). However, it dropped to 3.9 °C (39 °F) in August 1995.
On the warmest days of the month, the temperature usually reaches around 33 °C (91.5 °F). However, it reached 37.2 °C (99 °F) in August 2003.
Precipitation amounts to 60 mm (2.4 in), distributed over 8 days.
The day lasts on average 14 hours and 5 minutes. So the days are long.
There are on average 8 hours of sunshine per day. So, the sun shines 57% of the time.
The average humidity is 64%.
The average wind speed is 9 kph (5 mph).

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September is generally a very mild month. The average temperature is of 16.2 °C (61 °F), with a minimum of 10.3 °C (50.6 °F) and a maximum of 22 °C (71.6 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 5.5 °C (41.5 °F). However, it dropped to 1 °C (33.8 °F) in September 1995.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 28 °C (82.5 °F). However, it reached 33 °C (91.4 °F) in September 2009.
Precipitation amounts to 40 mm (1.6 in), distributed over 6 days.
The day lasts on average 12 hours and 30 minutes.
There are on average 7 hours of sunshine per day. So, the sun shines 55% of the time.
The average humidity is 69%.
The average wind speed is 8 kph (5 mph).

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October is generally a mild month. The average temperature is of 11.5 °C (53 °F), with a minimum of 6 °C (42.8 °F) and a maximum of 16.9 °C (62.5 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 0.5 °C (32.5 °F). However, it dropped to -4.6 °C (23.7 °F) in October 1997.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 23.5 °C (74 °F). However, it reached 28 °C (82.4 °F) in October 2009.
Precipitation amounts to 40 mm (1.6 in), distributed over 6 days.
The day lasts on average 10 hours and 55 minutes.
There are on average 5 hours of sunshine per day. So, the sun shines 48% of the time.
The average humidity is 74%. Hence, the air is normally humid.
The average wind speed is 6 kph (4 mph).

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November is generally a quite cold month. The average temperature is of 5.5 °C (42 °F), with a minimum of 1 °C (33.7 °F) and a maximum of 10.1 °C (50.2 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around -4.5 °C (23.5 °F). However, it dropped to -12.3 °C (9.9 °F) in November 2005.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 18 °C (64.5 °F). However, it reached 21 °C (69.8 °F) in November 2008.
Precipitation amounts to 50 mm (2 in), distributed over 7 days.
The day lasts on average 9 hours and 25 minutes.
There are on average 3 hours of sunshine per day. So, the sun shines 33% of the time.
The average humidity is 76%. Hence, the air is normally humid.
The average wind speed is 6 kph (3 mph).

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December is generally a cold month. The average temperature is of 1.3 °C (34 °F), with a minimum of -2.5 °C (27.4 °F) and a maximum of 5.1 °C (41.2 °F).
On the coldest nights of the month, the temperature usually drops to around -8.5 °C (17 °F). However, it dropped to -12.6 °C (9.3 °F) in December 2005.
On the warmest days of the month, the temperature usually reaches around 12 °C (53 °F). However, it reached 17.5 °C (63.5 °F) in December 2003.
Precipitation amounts to 70 mm (2.8 in), distributed over 8 days.
The day lasts on average 8 hours and 40 minutes. December 21, the winter solstice, is the shortest day of the year in the Northern Hemisphere.
There are on average 2 hours of sunshine per day. So, the sun shines 25% of the time.
The average humidity is 80%. Hence, the air is normally humid.
The average wind speed is 5 kph (3 mph).