Snow reliability

„No snow, no show“ - This sentence has the status of a principal in the industry. But from the visitors' point of view, what does snow reliability actually mean? We are currently in the process of finding out. Here you will find a survey, please let us know your opinion on the subject of snow reliability!

It is a fact: In modern ski areas, natural snow conditions hardly play a role for providing snow-covered pistes thanks to technical snow-making. For this reason, analyses of snowfall and the number of days of snow cover are not as relevant anymore.

As a skier, you want the ski area to function properly and all its areas to be accessible on a sufficient, well-maintained white surface. Sufficient natural snow on slopes that are not covered by technical snowmaking, powder in open terrain and snow-covered trees are of course a desirable bonus, but in case of doubt skiing only on technical snow is always better than not skiing at all - especially for the holiday guest. Some people book months in advance when there is no way of predicting what nature will deliver at the time of the trip.

The concept to valuate the snow reliability

There are a number of factors that influence whether and to what extent pistes are available in a ski area:

  • Quantity and frequency of natural snowfalls
  • Proportion of runs with technical snowmaking
  • Snowmaking performance (depending on hourly water flow per hectare, number and performance of snowmaking machines, air and water temperature, total available water volume etc.)
  • Proportion of glaciated terrain
  • Snow requirements of the terrain (rocky or meadowy ground)
  • Character of phases of thawing depending on exposure and local climate
  • Quality and intensity of snow management (use of snowmaking windows, piste maintenance, snow depots, snow fences etc.).

However, the valuation of snow reliability is not based on these factors, which combined produce the product snow on the slopes. Why? On the one hand, it would be virtually impossible to systematically assess the extremely complex interaction of these factors. On the other hand, it would be a unreasonable effort to collect the large amount of data for all relevant ski areas.

Therefore the snow safety should be evaluated primarily on the basis of the result, i.e. on the basis of what the guest experiences. What does the guest perceive? On the panorama display at the bottom station, the guest can see how many pistes are open, whether there is snow next to the pistes and whether it is possible to ski in the open terrain at the top of the mountain. He does not see whether the snow on the pistes has been produced by a machine, fallen from the sky or whether there is a glacier underneath.

Therefore, we first valuate the snow reliability on the basis of these three central factors:

  • Factor 1: Availability of open pistes
    What proportion of its terrain does a ski area usually provide at what times? Have there been days without skiing on important dates? On how many days could snow sports be practised in total? For the guest, it doesn't matter whether a ski resort achieves these results thanks to snowfalls or thanks to expensive technology, the guest simply wants to be able to practice his sport without any problems. In addition to the snow, the weather also plays a role, because especially in the high mountains, days of rest rarely result from a lack of snow, but often from storms or avalanches.
  • Factor 2: Number of snow cover days in the village
    If you spend several days in a winter sports resort as a guest, you also expect to find a winter atmosphere. At least most guests appreciate it when there is snow in the village.
  • Factor 3: Quantity of snow in the terrain (expressed by the annual sum of fresh snow)
    Since many snow sports enthusiasts are also looking for an off-piste powder experience, the natural amount of snowfall should also be included in the evaluation. Which weight you attach to it depends strongly on individual preferences and ability. For beginners, fresh snow is a problem even on the piste, for passionate freeriders there can't be enough of it.

The following variables are included in the valuation of these three factors:

Availability of open pistes in the last 5 winters

  • Availability in the core season: It is assumed that the season runs from December 20th to April 10th (average Easter Sunday), which means 112 days. The respective proportion of the open pistes (from zero to 100 per cent) is determined for each day of the period, which adds up to 112 values that are divided by 112 afterwards. The result is the average of open pistes over the entire period in percent. The availability of open pistes can be expressed by the proportion of open piste kilometres (e.g. 30 of 40 kilometres = 75 per cent), the area (250 of 500 hectares = 50 per cent) or the open lifts (7 of 10 = 70 per cent).
  • Availability during the Christmas holidays: The proportion of open pistes between December 25th and January 6th is determined in the same way. The percentage of open pistes and the percentage of days with ski operation in this period (e.g. 10 of 13 days = 77 per cent) are each weighted at 50 per cent. This takes into account the fact that it is particularly important at Christmas to be able to ski at all.
  • Total duration of the season: Ski resorts with high snow reliability are characterised by a long season. A season duration of 180 days means 100 per cent, which means that a maximum of 200 per cent can be achieved in year-round operation. The availability of at least one run is crucial.

Number of snow cover days in the village

  • For this purpose, official data from the weather services on the average number of days with snow depth >0 cm (in the last five winters) can be used. In the case of large ski resorts, which include villages at different altitudes (in the French Trois Vallées this ranges between 600 and 2300 metres above sea level), the altitude at which the bed capacities are concentrated is the relevant factor.
  • In addition, the average maximum snow depth in the village could be used. Thus, places that make the dream of snow to the edge of the roof come true would be appreciated accordingly. There are a number of winter sports resorts in which there is snow all the time but there is never a thick layer of snow.

Quantity of snow in the terrain

  • For this purpose, official data from weather services and ski resorts on the average annual sum of fresh snow are used. Certain distortions caused by different measurement methods have to be accepted. While European weather services measure the amount of fresh snow only once a day, elsewhere this is done hourly. The more frequently one measures, the higher the sum of fresh snow.
  • Of course it would be desirable to include other variables in this context: the number of days with at least 10, 20 or 30 cm of fresh snow, the quality of the snow (expressed by the air content of the snow layer), the maximum snow depths reached or the number of days with snow layers of more than two or three metres. However, as these data are not available on a broad basis and their collection would involve an unreasonable effort, they will not be available for the moment.

In addition to the three central factors, two bonus factors are to be included in the valuation:

  • the performance of the snowmaking system and
  • the proportion of glaciated terrain in the overall terrain.

Technical snowmaking

The efficiency of technical snowmaking is already indirectly taken into account via the availability of open pistes, because the more snowmaking is used, the higher the proportion of open pistes. Nevertheless, a high-performance snowmaking system is supposed to score points beyond this effect in the valuation of snow reliability. The reason for this is: technical snowmaking gives snow sports enthusiasts the luxury of skiing even in regions with insufficient natural snow reliability, regions which may be less far away and therefore enable us to make day trips. For this luxury the ski resort operators have to make an enormous financial effort. For the guests it is a valuable asset.

In this respect, expensive snowmaking can play a role in determining the value of a ski area. The capacity can be expressed by the pumping capacity (in cubic metres of water per hour) per hectare covered with artificial snow. This can be used to calculate how long it takes, for example, to produce 40 centimeters of snow in these areas. The faster, the better.

In order to assess the actual efficiency of the snowmaking system, the hours required for basic snowmaking should be related to the local climate. If, as in Finnish Lapland, you have reliable night-time lows of minus 10°C from November onwards, you can take a little more time for snow-making confidently. In German low mountain ranges, it is a blessing to have 40 or 50 hours of sufficiently cold temperatures before Christmas. However, efficiency is already taken into account by the availability of open pistes. That's why this bonus criterion is purely about the absolute power of snowmaking.

Glaciated terrain

Scheme of the snow reliability valuation

The situation with glacier ski areas is similar to that with snow-making. They offer the opportunity to ski or snowboard in autumn and well into spring - also a luxury. However, the operation of a glacier ski area involves an enormous amount of effort: Lift towers have to be moved, crevasses closed, avalanches triggered, wind fences set up and areas threatened by ice shrinkage covered in spring. Therefore, the existence of skiable terrain on a glacier also justifies extra points for snow reliability.

Overall, the concept for assessing the snow reliability is shown in the adjacent figure.

The method described above also requires a great amount of data that is recorded continuously. Since the 2018/19 season, initial results have been available for the reliability of supply in numerous ski areas. Using some of these ski areas as examples, the following table shows how a value for snow reliability can be determined.

Ski area

Basic factors

Bonus factors


(Benchmark 141,5% set 100%)


Freeride opportunities

Winter atmosphere

Glaciated terrain

Technical snowmaking

Availability of open pistes (2018/19 season)

Season duration

Snowfall mountain

Snow cover days village

Piste area

m³ per ha total area










671 cm


0 ha






668 cm


0 ha



Skiliftkarussell Bremberg



220 cm


0 ha






1,870 cm


9 ha




The weighting is currently still being verified in a survey. Some of the data in the table are still based on estimates.