Hot days, frost days and other climate indicators

Climate is more than just temperature and precipitation. MeteoSwiss makes available a broad spectrum of climate indicators that describe the climate, such as hot days and frost days, and serve to illustrate how the climate is changing. They help professionals and planners to make sense of climate change, and to take it into account in the context of decision-making and practice.

Climate indicators are parameters that are derived from meteorological measurement data, such as temperature and precipitation. Each one focusses on a specific aspect of climate (such as heat waves, frost or drought). Climate indicators thus portray the current climate in a very clear and easily understood way. Furthermore, historic and future developments of the climate can be analysed in such a way that is suited to the user's individual needs. Answers can thus be provided to questions which have relevance to the "real world" - such as "Are we having more hot days now than we did 50 years ago?" or "Are the winters really not as cold nowadays?" or "How many days with fresh snowfall will there be in 2060?".

Hot days

Hot days are defined as days in which the temperature rises above 30°C. The number of such hot days in Switzerland has been rising continuously over the past few decades, as illustrated in the example of the Lucerne station, where the number of hot days has been rising year on year. Whereas there were a maximum of 10 hot days per year up until the beginning of the 1980s in Lucerne, over the past 15 years, this figure has risen considerably, reaching more than 25 days in certain years. In Lucerne, there has not been a single year without a hot day since 1980.

There are many of us who are happy to have higher temperatures and a chance to swim in the lakes. Others suffer in the heat, however, and those who are sick or elderly are particularly affected by hot weather. Changing heat event patterns are regarded as important by the building and civil engineering industries, where steps are being taken to develop and implement solutions for achieving comfortable living and working environments (e.g. better insulation and appropriate air conditioning).

Frost days

Days on which the temperature falls below 0°C are known as frost days. The number of frost days across Switzerland as a whole is steadily decreasing. As the example of Davos illustrates, the number of frost days has decreased significantly, falling by around 20% over the past 40 years.
Data on frost days are useful in fields such as the winter sports industry, in which providers are able to utilize the information on the changes in frost-day occurrences for their seasonal planning and future investment decisions.

Dryness


Dryness occurs when there is no precipitation for an extended period of time. In combination with high temperatures, dryness in summer leads to drought, which can have a negative impact on agriculture, for example. Dry winters lack the snow and rain needed to fill the reservoirs for spring and summer, as well as presenting a challenge for snow sports.

There are various indicators for dryness, one of the simplest being the number of consecutive days without precipitation. Taking the examples of the Geneva, Basel, Locarno and St. Gallen stations, the graph shows that the dry period patterns in different locations across Switzerland have developed in different ways. In some areas, such as Geneva and Locarno, the dry periods have become longer, whereas in Basel, the exact opposite is the case. In St. Gallen, on the other hand, there has been no change over the long term.

Want to know more? Climate and drought indicators

A wide range of climate  and drought indicators are available on the MeteoSwiss website under the heading "Climate indicators" as well as “Drought indices”, where the developments in these indicators over the past few decades can be viewed for different seasons and time periods under the meteorological station selected by the user. The information can also be downloaded in PDF format if required.

Climate indicators

Climate indicators are parameters used to characterise the climate. The change in important indicators can be illustrated graphically for measuring...

Drought indices

Drought indices from MeteoSwiss describe current drought or wetness at selected sites and compare the current situation with long term records.