Netherlands records first official summer day of 2026 as temperatures rise toward 30°C
The Netherlands recorded its first official summer day of 2026 on Friday, May 22, when temperatures in De Bilt reached 25.0°C. Warm, sunny conditions are expected to continue into the coming days, with forecasters predicting a hot and mostly dry run-up to the Pentecost holiday period. According to weeronline, inland temperatures are expected to reach 26–29°C, with local peaks up to 30°C in the south.
At 3:40 p.m. on Friday in De Bilt, the national meteorological reference station used for official Dutch climate measurements, temperatures reached 25.0°C, marking the first official summer day of 2026. The event came slightly later than average based on the 1996–2025 climate period, which places the first 25°C day around May 15.
Warm conditions were widespread across the country. Eindhoven recorded 27.2°C, the highest temperature of the day. Earlier in May, summer-level warmth had already been measured at several locations, including 25.6°C in Gilze-Rijen, 25.3°C in Woensdrecht, 25.2°C in Hoek van Holland, and 25.1°C in Ell (Limburg) on May 1. De Bilt reached 23.6°C on that same day.
Forecasts indicate that warm, sunny weather will continue in the days ahead. On Saturday, inland temperatures are expected to reach 26°C to 29°C, with local peaks up to 30°C in the south. Coastal areas will be cooler at 20°C to 23°C due to sea breezes, while the Wadden Islands remain between 18°C and 22°C.
On Sunday, during the Pentecost holiday period, conditions remain sunny and warm across much of the country. Inland temperatures are expected to range from 22°C to 28°C, with the highest values in the south. Northern coastal areas and the Wadden Islands stay cooler at around 19°C to 21°C, with occasional light sea breezes again providing relief along parts of the western coast.
On Monday, also part of the Pentecost holiday period, sunny and dry conditions continue. Inland temperatures are expected to reach 25°C to 28°C, while northern and coastal regions remain cooler at 18°C to 20°C under the influence of northerly winds and the relatively cold North Sea.
Tuesday is forecast to bring another sunny and warm day, with highs of 25°C to 30°C across central, eastern, and southern regions. Northern and western coastal areas will remain cooler at 22°C to 25°C. The North Sea, at around 13°C, continues to suppress temperatures along the immediate coast.
After Tuesday, a brief cooldown is expected as cooler air moves in from the north to northeast. Wednesday brings temperatures of around 16°C in the north and 19°C to 21°C elsewhere. Thursday becomes slightly milder at 18°C to 23°C. From Friday onward, temperatures are expected to rise again toward 20°C to 25°C, with conditions remaining dry and sunny.
The first summer day coincides with the rollout of a new “heat intensity” index developed by the Royal Netherlands Meteorological Institute (KNMI). The system will be introduced in the KNMI app on June 2 and is designed to better reflect how heat is experienced by combining temperature, humidity, wind, and solar radiation into a single scale from 0 to 10.
The index is based on wet-bulb globe temperature and typically ranges from 3 to 6 in summer conditions. A maximum value of 10 has never been recorded in northwestern Netherlands, and in De Bilt it has only occurred for about four hours across three days in 2005 and 2019.
KNMI researcher Carolina Pereira Marghidan said: “Niet elke 25 graden is hetzelfde, dat weten we denk ik allemaal uit ervaring,” translated as, “Not every 25 degrees is the same, I think we all know that from experience.”
She added that perceived heat varies strongly depending on conditions: wind and cloud cover reduce heat stress, while full sun and humidity significantly increase it because the body cools less effectively through sweating.
TNO researcher Boris Kingma, who helped develop the index, said: “Dezelfde hitte is voor de een wel een probleem en voor de ander niet,” translated as, “The same heat is a problem for one person and not for another.”
He explained that the body cools by widening blood vessels, which increases strain on the heart. People with cardiovascular conditions or lower fitness levels may therefore experience greater difficulty in warm conditions, and physical activity can turn otherwise moderate heat into a risk.