The Netherlands is in for several very hot and very humid days, with temperatures up to 35 degrees Celsius and thunderstorms expected in some places. The KNMI issued a code yellow warning for “an unpleasant, oppressive heat,” covering the entire country except the Wadden Islands from 10:00 a.m. today until at least Saturday. The National Heat Plan also takes effect at 10:00 a.m.

“The combination of high temperatures and humidity creates an unpleasant oppressive heat,” the KNMI warned. “The elderly and people with vulnerable health may experience health problems as a result. However, anyone can experience symptoms such as dehydration and overheating during strenuous physical activity.”

On Thursday, maximums will range between 27 and 32 degrees. Friday will be even hotter, with temperatures of 30 to 35 degrees Celsius. “The forecast for the weekend remains uncertain, but it is likely to remain persistently very hot, especially in the southeast,” the KNMI said. “On Monday, temperatures may reach 30 to 35 degrees Celsius again throughout the country. Partly due to high humidity, the maximum heat index will consistently remain between 7 and 9, particularly in the southeast.”

The high humidity and heat combined translate into a chance of thunderstorms overnight tonight and on Friday afternoon and evening. “Locally, showers could be severe with a very localized chance of hail and strong wind gusts,” the KNMI said about Friday. “However, this is still uncertain.”

The National Institute for Public Health and the Environment (RIVM) will activate its National Heat Plan at 10:00 a.m. on Thursday. Caregivers and healthcare professionals are urged to pay extra attention to vulnerable groups, including elderly people and small children. The RIVM recommends providing easy access to drinking water, limiting outdoor activities to the cooler parts of the day, and taking measures to keep indoor spaces as cool as possible.

Dutch residents are also urged to check on vulnerable neighbors because of the heat.