In May 2025, an extraordinary heatwave descended upon Iceland and eastern Greenland, marking a climatic anomaly that caught the attention of scientists and residents alike. On May 15, Egilsstaðir Airport recorded a staggering 26.6°C, setting a new national record for the month. This was just one of many weather stations that reported temperatures soaring as much as 13°C above the average for that period, which spans 1991 to 2020.
Lasting around nine days, this heatwave distinguished itself not only by its intensity but also by its unexpected timing and wide-ranging effects. While Iceland is no stranger to fluctuating weather patterns, the scale and duration of this event raised eyebrows and prompted inquiries.
An international consortium of scientists from the World Weather Attribution initiative, including experts from the Icelandic Meteorological Office, as well as institutions in the Netherlands, Denmark, Sweden, the United Kingdom, and the United States, conducted a thorough analysis aimed at understanding how human-induced climate change played a role in this heatwave. Focusing specifically on the seven hottest days in May, their assessment unveiled some startling insights.
The findings revealed that climate change had made this heatwave approximately 40 times more likely and, on average, three degrees Celsius hotter than it would have been in a pre-industrial climate. Although there is inherent uncertainty in these estimates, the consensus among scientists is clear: climate change significantly increased both the probability and intensity of such extreme weather events.
This analysis was based on comparisons between the observed temperatures during the heatwave and results generated from climate models. Alarmingly, these models indicate that if global warming escalates to 2.6°C later this century, heatwaves of this magnitude could become at least twice as frequent and, on average, two degrees warmer than we experience today.
Currently, with the climate having warmed by approximately 1.3°C since pre-industrial times, heatwaves of this nature carry a 1% annual chance of occurrence. In practical terms, this means such an event could be expected roughly once every century. In a cooler, pre-industrial context, events of this severity would have been nearly absent from Iceland’s recorded history.
The complete analysis from World Weather Attribution is accessible here.
For additional details on the May heatwave in Iceland, click here.
