The Netherlands

‘1001 Hot Nights project’

Research into Nighttime Heat

Due to climate change, we are experiencing heat more frequently and for longer periods. Prolonged heat causes buildings and homes to warm up, making it difficult for residents to cool down at night and get a good night’s sleep. This can lead to negative effects on health, work productivity, and overall quality of life. Through the 1001 Hot Nights project, Weather Impact and its partners are conducting further research into nighttime heat.

Currently, there is insufficient practical knowledge about how often and where nighttime heat occurs. A better understanding and interpretation of nighttime heat has been needed for several years, among other reasons to explain health issues in different urban neighborhoods and to determine which mitigation measures are necessary and where they should be implemented most effectively. Insight into nighttime heat is also essential for establishing heat standards for existing buildings. Finally, improved knowledge of nighttime heat is needed for the development of new climate stress tests.

The 1001 Hot Nights (2025-2026) project therefore aims to investigate how often and where this phenomenon occurs, both now and in the future. The project also examines which temperatures residents consider unacceptable, which spatial factors influence nighttime heat, and which measures in urban areas and residential buildings can help reduce its impacts.

How will the results of the 1001 Hot Nights project be used?

Researchers will use these insights and findings to develop recommendations and guidelines, together with and for practitioners such as municipalities and housing associations, on how to improve cooling in homes and outdoor spaces. The project’s results will form the basis for new heat stress assessments and the development of local heat action plans.

Within the project, Weather Impact is responsible for conducting the meteorological research. In this role, we contribute to both the spatial and temporal analysis of meteorological data.

Results night heat

The first results show that the average nighttime temperature at many locations is 23°C, and in cities it can reach 25°C. Under the current climate, this occurs only once or twice per year, but with climate change, we can expect these extreme temperatures to occur much more frequently in the future.

Figures 2 and 3. The figure on the left shows the average number of warm evenings per year, with temperatures above 20°C between 8:00 PM and 11:00 PM. Elevated evening temperatures can have a greater impact on indoor temperatures than nighttime temperatures, as homes are often ventilated during the evening hours.

The figure on the right shows the average number of warm nights per year.

Project Partners of 1001 Hot Nights

The 1001 Hot Nights project is being carried out on behalf of the Ministry of Infrastructure and Water Management and is financially supported by Tauw Foundation and the provinces of Utrecht, Gelderland, Overijssel, North Holland, South Holland, North Brabant, and Zeeland.

Partners within the project are Hogeschool van Amsterdam (lead), KNMI, Climate Adaptation Services, TAUW and Weather Impact.

Extreme precipitation forecasts & flood warnings

Weather Impact partnered with the Dutch Royal Meteorological Institute (KNMI) to develop an operational warning system for extreme precipitation (2019-2021). The warning system uses innovative statistical techniques on ensemble forecasts and radar nowcasts to generate a combined precipitation forecast at high resolution in place and time. According to the requirements of the specific user, a warning is generated if the forecasted precipitation exceeds the user–specific thresholds. The KNMI focusses in their part on improving the stochastic forecasts of their radar nowcasting product (0 till +2 hours) and HARMONIE short term weather forecasts (0 till +48 hours). Next to an improved forecast of extreme precipitation, a warning system should also be user-friendly and flexible for various end-user groups. Weather Impact investigated the user needs and performed a cost-loss analysis to optimize the warning system. During a one-year trial period in 2021, different extreme precipitation events occur in the Netherlands. These cases have been analyzed and published.

Together with a dozen waterboards, municipalities and Hydrologic, we started a public-private partnership; W2O innovation project (2021-2026). W2O stands for Waarschuwing voor WaterOverlast and is a flooding alert service for government organizations in the Netherlands. Within this project we aim to further develop and improve the service, by offering a localized and more accurate forecast. This way we help the users in their decision making to prevent damages and losses.

More information about the extreme precipitation project and the W2O innovation project can be found on our Dutch website.

Design of an hail-alert system for insurance

In the Netherlands, summer hail with a diameter of two centimetres or more occurs a few times a year somewhere in the country. Larger hailstones, varying from 6 cm to more than 10 cm, come down almost every summer. The hailstorm of June 23, 2016 that passed over the South-eastern part of the Netherlands caused an estimated damage of about 500 million euros. The Dutch Association of Insurers, in collaboration with the KNMI, demonstrated that intense rain and hail showers will cause much more damage in the future climate. Further adaptation to future climatic patterns is needed. To become more climate resilient in the long term, the best way is to keep premiums affordable and insurable is to take preventive measures. A short-term hail notification could support for example car-owners to protect their assets from hail.

In this feasibility study, commissioned by the Dutch insurance company InShared, Weather Impact and Disdrometrics explored the possibility of developing an operational hail-alert system. An operational, full automatic system was designed that warns clients of InShared when they are present in a high risk area.

Workshops

Weather and water management

This course offers practical knowledge about the weather and weather forecasts, which is for example of great importance when calculating the water level to take preventative measures. The course focuses on practical cases with weather data and water level management. After this course you are better prepared for future climate and do you know how to take the weather aspects into account in your advice and measures in daily water management.

Extreme weather and climate

This three-day training gives lots of insight on climate change and its impact and consequences on the physical living environment. Relevant cases and practical experiences provide a strong link to policymaking.

Customized training

We also offer customized training, right what is required for your organization.

For more information about our work in the Netherlands, see our Dutch website www.weatherimpact.nl