Mountain weather: where to find official forecasts and how to read them

Why the village forecast tells you nothing about the pass

On your phone: blazing sunshine and 18 °C in the village. The pass you are heading for sits 2,000 m higher, and that is where you will spend the day. Temperature drops by an average of 0.65 °C every 100 m, according to MeteoSwiss [1]: at 3,000 m, those 18 °C become about 5 °C, before the wind has had its say. The app was not lying; it was simply talking about the village.

There are exceptions. In fine autumn or winter weather, a temperature inversionA situation where temperature rises with height instead of falling, often beneath a sea of cloud or valley fog. can make the air milder at 2,500 m than on a valley floor at 500 m [2]. The Met Office sums up the difficulty: in the mountains, the weather can vary dramatically from one hour to the next and from one hill to the next [3].

Hence mountain forecasts. National weather services use them to give values where you will actually be walking: wind on the ridges, temperature at 2,000 or 3,000 m, the height of the freeze. Here is where to find them in each country our editions cover, followed by what their terms mean, as the services themselves define them.

France: Météo-France’s mountain section and its Vigilance map

Everything starts on Météo-France’s Météo Montagne page. It is divided into seven regions, from the Northern Alps to Corsica by way of the Pyrenees, the Jura, the Vosges and the Massif Central, with forecasts by resort, snow cover and snow depths [4]. Each region lists its forecast points, some of them at height: the Northern Alps page offers, for instance, ‘Chamonix Mont-Blanc 3845m’ and ‘La Plagne 3250m’ [5].

Météo-France also describes a mountain safety bulletin, the Bulletin Sécurité Montagne, published every day at 5pm for that day and the next, and for the day after that too in the Alps, Corsica and the Pyrenees. It is written by department in those three regions and by massif in the Vosges, the Jura and the Massif Central, with a height threshold above which it applies. It flags phenomena that exceed a threshold specific to the mountains, such as thunderstorms, heavy precipitation, strong wind, cold or fog, then gives precipitation, wind on the ridges or at a given height, with its gusts, and temperatures at reference heights, including the 0 °C isotherm where useful [6].

One caveat about the Bulletin Sécurité Montagne: the page that presents it, the one for the Vosges, sits in Météo-France’s ‘prototype workshop’, whose products are experimental and do not replace its official output [8]. Its method is nonetheless a useful guide to reading any mountain forecast, and we will come back to it.

Switzerland, Austria and Germany: three services and an Alpine club

Switzerland: MeteoSwiss

MeteoSwiss publishes hour-by-hour local forecasts together with their uncertainty: a curve for the median scenario and, around it, a band containing 80% of the calculated scenarios [9]. The wider the band, the less certain the forecast. Its warnings follow the five-level scale of the federal natural hazards services, from green (‘no or low danger’) to dark red (‘very high danger’); the portal points out that levels for two different hazards cannot be compared directly [10].

Austria: GeoSphere Austria

In Austria, the national service is called GeoSphere Austria. On its forecast page, a menu lets you choose a province: the forecast text changes accordingly, including a Bergwetter, or mountain forecast, where one exists for that province [11]. Its warnings are ‘impact-based’: they take account of wind speed, rain or snowfall, but also of the season, the time of day and whether the trees are in leaf [12]. GeoSphere also runs an observatory on the summit of the Hoher Sonnblick, at 3,106 m [13].

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Germany: the Deutscher Wetterdienst

The Deutscher Wetterdienst (DWD), Germany’s national weather service, publishes a forecast for southern Bavaria every day at 10.30am, with temperatures at 2,000 and 3,000 m and the snowfall limit [14]. Its warnings have four levels, yellow, orange, red and violet, plus a hatched advance notice when a very dangerous spell is on the cards but its area, timing and intensity are not yet certain enough [15]. One detail matters in the mountains: on exposed summits, gust warnings are decided case by case [16].

The German Alpine Club’s Bergwetter

The German Alpine Club publishes a Bergwetter for 17 regions of the Alps, with headlines written by GeoSphere Austria meteorologists. Since May 2026, each region has a table in 6-hour blocks: temperatures at typical heights, mean wind and gusts, snowfall limit, 0 °C isotherm, and the likelihood of precipitation, thunderstorms and fog on a scale of 0 to 3. Its values apply to open, exposed places such as ridges and passes [17].

United Kingdom: the Met Office and MWIS

The Met Office publishes mountain forecasts for ten areas, from the Northwest Highlands to the Brecon Beacons by way of the Lake District and Eryri, or Snowdonia [3]. They come out every afternoon before 6pm, cover the evening, then two days in detail and a three-day outlook, and are updated before 6am [18].

Each forecast opens with nine hazards specific to the mountains, each rated with a nil, low, medium or high likelihood, which apply at or above 300 m; a mountain hazard can be in force with no weather warning for the same area. Next comes a table of wind, gusts, temperature and ‘feels like’ temperature, from valley to summit, followed by a text written by a meteorologist [18]. The national warnings, yellow, amber or red, combine the likelihood of the event with its expected impact [19].

United States: the National Weather Service point forecast

On weather.gov, the National Weather Service (NWS) offers a map on which you click the spot you are heading for. The forecast you get applies to a square of about 5 km around that point [22], and the page shows the elevation of the forecast point (‘Elev.’): compare it with that of your objective, as it may be lower than the summit you have in mind.

Its alerts use three words. A watch means a hazard is possible, a warning that it is happening or imminent, and an advisory that it is less severe than one calling for a warning. The thresholds are not national: each local NWS office sets its own criteria [23].

Isotherm, snowfall limit, freezing level: three heights that get mixed up

The 0 °C isothermThe height at which the air temperature reaches 0 °C: below it the temperature is positive, above it negative. separates air above freezing, lower down, from air below freezing, higher up. Météo-France describes it as an imaginary surface, usually fairly flat, which forecasters call the ‘iso 0’ among themselves [24]. The one in forecasts is not the one on the ground: MeteoSwiss distinguishes the isotherm in the free atmosphere, measured by weather balloons, from the one derived from ground stations, and its forecasts give the former. Near the ground, temperature can vary a great deal over a short distance, especially in the six winter months [25].

The snowfall limitThe theoretical height at which as many snowflakes as raindrops are falling. Météo-France calls it the rain-snow limit. lies lower, often 200 to 400 m below the 0 °C isotherm, according to both Météo-France and MeteoSwiss [26, 2]. A reminder that has saved many an evening: it is not the height at which snow settles, which is generally 50 to 200 m higher [26]. And in heavy precipitation, snow can fall much lower, as much as 800 m below the 0 °C isotherm according to Météo-France [26].

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In Britain, beware a false friend. In Met Office mountain forecasts, the freezing level is not the air isotherm: it is the level above which snow is expected to settle, or the ground to be frozen, without allowing for surfaces melting in direct sunshine during the day [18]. The US National Weather Service uses the same term for the height at which the air temperature first drops below freezing [27], in other words the 0 °C isotherm.

‘30% chance of rain’: one figure, several definitions

The chance of rain is the most-read figure in any forecast, and one of the most misunderstood. None of the services quoted here takes it to mean rain for 30% of the time, but they do not all calculate it the same way. At MeteoSwiss, it is rather like asking ten neighbours: if three of them take an umbrella, the forecast says 30%. The neighbours, in this case, are scenarios calculated by the models from slightly different starting conditions [9].

Two points apply whatever the service. In thundery weather, calculated probabilities are lower than for widespread rain, because showers fall in patches, and if a shower does hit the forecast spot, the median amount given is often well short of the mark, MeteoSwiss warns [9]. As for thunderstorms, the German Alpine Club defines them simply: there is a thunderstorm when thunder can be heard, and strong storms, with hail and squalls, remain possible even when the likelihood is low or moderate [17].

Mean wind, gusts, summits in cloud: the other words in the forecast

Mean wind is, by convention, an average over 10 minutes, measured 10 m above the ground. A gustA sudden increase in the instantaneous wind that exceeds the mean wind by more than 10 knots (18 km/h), according to Météo-France. is all the stronger when the air is unstable, the mean wind is strong or the terrain disturbs the airflow [24]. In mountain forecasts, wind is given at a set height or at ridge level [6]. The German Alpine Club points out that strong gusts can blow even when the mean wind stays moderate [17], and the Met Office that the strongest winds it quotes are normally found on exposed peaks and ridges [18].

British forecasts add a section that walkers tend to read first: the chance of cloud-free tops, or, as the Met Office puts it, the chance of your efforts being rewarded with a view from the summit, with the extent and persistence of low cloud across the area [18]. MWIS gives it as a percentage [21]. There is more at stake than the photograph: the Met Office lists poor visibility among its mountain hazards, with low cloud or snow often cutting visibility to 50 m or less [18].

Reading a forecast without asking it to decide for you

A forecast describes the expected weather over an area; it does not tell you whether your walk will go. Météo-France says so in black and white: its mountain bulletin provides neither a risk assessment for any given activity nor advice, and it is up to each user to assess the risk in the light of their activity, exposure, experience and equipment, then decide whether to go ahead, adapt or turn back [6].

A few habits help. Check the date and time of issue, as a forecast can be amended before the next scheduled one [6]. Note the area and the height it applies to: actual conditions can differ markedly from the regional forecast on steep ground, in valleys or in very exposed spots, the German Alpine Club reminds us [17]. And do not stop at the symbol: the Met Office notes that it will not be representative of conditions everywhere, and that a hazard affecting only a small part of the area is often given a lower likelihood [18].

Finally, the forecast is read alongside what you know of the route. A route grading always assumes good weather and dry ground; a well-judged walking time tells you when you will be on the very ridge the forecast describes; the warden of a mountain hut knows the state of the path; and without a car, the time of the last bus is read alongside the forecast.

A good habit to get into: before the figures, read the forecast’s time of issue, its area and its height, then read it again on the morning you set off if it has been updated, as the Met Office does before 6am [18]. A forecast is like bread: best fresh that morning.

Guillaume Hoarau

Camping, wild camping, bushcraft and hiking

Guillaume Hoarau writes for Outfarer about camping, wild camping, bushcraft and hiking. A survival-skills enthusiast and a collector of old field manuals, he likes clear explanations, lists that earn their place and other people’s stories, which he tells well.

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