How forecasts, symbols and the Swiss climate work — so our pages tell you more.
How a forecast is produced
A forecast is the output of a numerical model: the atmosphere is divided into a grid of cells and the equations of physics are solved step by step for each one. We use the ICON model (German weather service) and IFS (European Centre), aggregated by Open-Meteo, at roughly 2 km resolution over the Alps — fine enough to tell a valley from a ridge. The models are re-run several times a day. Beyond seven days, treat the output as a trend rather than a forecast: the atmosphere is chaotic, and two nearly identical states diverge within a week.
Reading the weather symbols
Our icons follow the WMO codes, the World Meteorological Organization standard. "Rain" means continuous precipitation; "showers" means short, intermittent bursts, typical of afternoon instability in the mountains. "Overcast" means more than 87 % cloud cover, "partly cloudy" a mixed sky. Night icons show the moon: the same situation gets a different icon at 2 p.m. and at 11 p.m. A thunderstorm symbol flags a risk of hail and gusts even when the rainfall total stays small.
Switzerland's climate
Switzerland is temperate but highly compartmentalised. The Plateau has mild summers (22–26 °C on average in the afternoon in July) and cool winters with stubborn low stratus. In the Alps the temperature drops about 0.6 °C per 100 m: a 28 °C August day in the lowlands becomes 16 °C at 2,000 m. Ticino, in the south, gets the country's heaviest precipitation (often over 1,800 mm a year) while recording the most sunshine hours. Central Valais, sheltered by the Alps, is the driest region in the country.
Swiss microclimates
Two municipalities a few kilometres apart can have completely different days. The large lakes (Geneva, Constance, Neuchâtel) soften extremes and delay frost. In winter, temperature inversions trap cold air and fog in the hollows of the Plateau while mountain resorts sit in sunshine. The foehn, a warm dry wind descending from the Alps, lifts temperatures by several degrees in central and eastern Switzerland. The bise, by contrast, blows from the north-east across the Plateau and sharply increases the feeling of cold.
Understanding air quality
The index shown follows the European scale and combines fine particles (PM2.5, PM10), nitrogen dioxide and ozone. Two situations dominate in Switzerland: in winter, inversions concentrate particles in the valleys and on the Plateau; in summer, strong sunshine produces ozone, especially in the afternoon south of the Alps. "Good" or "fair" requires no precaution. From "poor" upwards, sensitive people (asthma, children, older adults) should avoid intense outdoor exercise at peak hours.
Weather and health
Rapid pressure changes often come with headaches and joint pain; it is the change, more than the absolute level, that people feel. The UV index rises about 10 % per 1,000 m of altitude and doubles with reflection off snow, so protection is needed in the mountains even when the air is cold. In a heatwave, drink regularly and move any effort to before 11 a.m. In hard frost with the bise blowing, the felt temperature can be 8 to 10 °C below the measured value.
Planning outdoor activities
On summer hikes, start early: convective thunderstorms usually break between 2 and 6 p.m. Check the forecast at summit altitude, not just the village — our pass and summit pages compute it. For skiing, the snow line and gusts decide the day: above 60 km/h lifts often close. On the lakes, watch the wind: a 25 km/h breeze quickly raises a chop that makes paddleboarding or light sailing awkward.
Making sense of warnings
MeteoSwiss, the official service, grades its warnings from 1 (low danger) to 5 (very high danger) for thunderstorms, rain, snow, wind, frost and heat. Level 3 signals significant danger: adjust your plans. Levels 4 and 5 describe rare situations where you should stay in. Our banner highlights notable conditions forecast in the main cities; it does not replace official warnings or instructions from local authorities.
Sources and reliability
Forecasts come from Open-Meteo, which aggregates the ICON and IFS models. The climate normals shown for each municipality are computed from official MeteoSwiss measurements (SwissMetNet network, 1991–2020): we interpolate the three nearest stations and correct for altitude. The rain radar comes from RainViewer. A forecast is roughly 90 % reliable at 24 hours, 75 % at three days and 50 % at seven days; beyond that it shows a trend. When there is danger, always follow the official MeteoSwiss warnings.