The Amersfoort half marathon will now take place in early spring because of rising temperatures in May and June. The next edition is set for April 4, nearly two months earlier than in recent years.

At the most recent Amersfoort Marathon on May 31, several runners became unwell because of the heat. One runner collapsed just before the finish line at Eemplein and required resuscitation, according to bystanders. Multiple ambulances were dispatched to the scene. Temperatures reached about 25 degrees Celsius in Amersfoort that day. Other running events have also recorded heat-related incidents recently.

The risk of heat and high humidity creates uncertainty for participants, suppliers, and the organizers themselves, according to the Marathon Amersfoort organization. That risk is smaller in early April. “We are very happy that we have made the decision,” Stichting Marathon Amersfoort chairman Jaco Uittenbogaard wrote in a statement.

About 9,000 people take part in Marathon Amersfoort. They run distances of 5, 10, or 21 kilometers, the last of which is a half marathon. A day earlier, organizers held a training marathon covering the classic 42.195-kilometer distance. It has no winner and is intended so runners “can cover the marathon distance at their own pace.”

Marathon Amersfoort is believed to be the first major event shifted earlier because of rising temperatures. Other organizers, including those of the Groningen Marathon, are considering similar moves, though not all see the possibility or necessity.

Stichting Marathon Amersfoort consulted sponsors and the municipality before deciding, since the new date also affects the deployment of emergency services and insurers. All involved parties support the change, race director Mik Borsten told NOS.

Public opinion also played a role, Borsten said. “If it goes wrong, you get the question sooner: how stupid can you be?”