Code Yellow and National Heat Plan Active in the Netherlands as Temperatures Hit 35°C
Hot, humid weather pushes the country into Code Yellow and activates the National Heat Plan from Thursday morning. The KNMI warns of "oppressive" conditions through Saturday to Monday.
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The Dutch national weather service KNMI has issued a Code Yellow warning for heat across nearly the entire country, while public health institute RIVM has activated the National Heat Plan, as the Netherlands moves into a stretch of hot, humid weather with temperatures rising to 35°C. The warning runs from Thursday morning, 18 June, through Saturday morning, with another peak expected on Monday.
What the forecast looks like
Code Yellow applies to all 12 Dutch provinces from 10 am on Thursday until 7 am on Saturday; only the Wadden Islands are exempt. According to the KNMI, Thursday will see maximum temperatures of 27 to 32°C, climbing on Friday to 30 to 35°C, with the highest values in the southeast. The combination of high temperatures and high humidity will give a “heat strength” (hittekracht) of 8 or 9 on a 10-point scale, which puts vulnerable people at risk and can also affect anyone doing physically demanding work.
The weekend forecast is still uncertain. Saturday is likely to bring 25 to 32°C and continued humidity, with chances of heavy thunderstorms; Sunday roughly the same, and Monday potentially another country-wide return to 30 to 35°C. Even at night, temperatures are not expected to drop below about 18°C, meaning houses, and bodies, will get little chance to cool down.
Cities, in particular, will heat up faster and cool down more slowly than the surrounding countryside, the KNMI notes, because of the urban heat island effect (the way buildings and asphalt retain warmth).
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The National Heat Plan
In parallel with the Code Yellow warning, the RIVM has activated the National Heat Plan (Nationaal Hitteplan). The plan is a warning system, rather than a measure on its own: it is intended to alert organisations in healthcare and welfare, informal carers, GPs and others who look after vulnerable people that a prolonged spell of heat is on the way. The Heat Plan is not the same as an official heat wave, which can only be confirmed afterwards (when, in De Bilt, the temperature has been at least 25°C for five consecutive days, three of which over 30°C).
The largest at-risk group is people over the age of 75, who are less able to regulate their body temperature and feel thirst less quickly. Also at higher risk are people with chronic conditions, very young children, pregnant women, people in social isolation, and the homeless.
Practical advice
The standing advice from the RIVM, when the Heat Plan is active, is to slow down in the warmest hours of the day, keep windows and curtains closed during the day and open them at night when temperatures drop, drink enough water (even without thirst), and check on elderly neighbours, young children and others who may have a harder time looking after themselves. People are also advised never to leave children or pets in a parked car, caravan or any other space that can heat up rapidly.
Outdoor sports and races are advised to plan starts in the early morning and have extra water, shade and medical staff on standby. Schools may introduce a tropenrooster (a tropical schedule with an earlier finish), with extra breaks, more ventilation and more frequent drink moments; in that case, parents should be informed and alternative care arranged for younger pupils. The quality of bathing water can also drop during prolonged heat, so swimmers are advised to check local advisories.
Storms and shifting weather
Despite the heat, the period will not be entirely settled. The KNMI is warning of a “heavy thunderstorm” risk in places on Thursday and Friday evening, with possible hail and gusty winds, and a similar risk on Saturday. After Monday’s expected peak around 35°C, the heat will probably ease, but a longer forecast still shows around a 70 percent chance of warm weather running into the following week.
For people in the Netherlands, in particular for the very young, the very old and people working outdoors, the basic message is the same as it has been for previous heat episodes this spring: take it slowly, drink enough, look out for others, and keep an eye on the KNMI app and weather reports for the latest warning level.