As calm seas enveloped Eyjafjörður near Akureyri on May 17, 2025, the region was experiencing an unprecedented meteorological phenomenon. In a town that boasts over a century of temperature records, the average temperature for the first 22 days of May stood at a remarkable 10.9°C—shattering previous records for this time of year. (Photo: IMO/Haukur Haraldsson)
- Temperatures soared to or exceeded 20°C across various weather stations for an unbroken stretch of 10 days.
- New May temperature records fell one after another at stations nationwide.
- A record-breaking high of 26.6°C was recorded at Egilsstaðir Airport on May 15.
From May 13 to 22, 2025, Iceland found itself in the grip of an extraordinary heatwave, a phenomenon driven by a persistent high-pressure system near the Faroe Islands that gradually drifted over the country. This atmospheric setup funneled warm air from the south and southeast, bringing uncharacteristically high temperatures and a sweeping brightness that enveloped the entire nation. While Iceland has seen similar weather patterns in the past, the duration, timing, and extensive reach of this heatwave marked it as exceptionally remarkable.
The warm spell led to widespread reports of temperatures exceeding seasonal averages, particularly in the northeastern and eastern highlands, where anomalies eclipsed 10°C. Even the typically cooler southern and southeastern coasts experienced anomalies of 3°C or more.
Figure 1: Temperature anomalies (°C) at automatic weather stations from May 13 to 22, 2025. Anomalies are calculated against the expected daily temperatures derived from the past decade (2015–2024).
Traditionally, May has been characterized by cool weather in Iceland, with temperatures rarely exceeding 20°C. In recent years, such highs have appeared for just 2 to 3 days each May. However, this year broke the mold, as temperatures crossed the 20°C threshold for ten consecutive days between May 13 and 22, and even climbed to 20°C on May 7—totaling 11 warm days so far this month.
During the weekend of May 17–18, temperatures peaked dramatically, with about half of all weather stations recording highs of 20°C or more. The national average temperature also hit unprecedented heights during this period.
The first three weeks of May 2025 have stood out not just in memory but in measurement. Remarkably, only two days saw slightly below-average temperatures when contrasted with the last ten years of climate data. Weather stations with extensive historical records, such as Stykkishólmur (data since 1846), Reykjavík (since 1881), and Dalatangi (since 1939), showed similar trends. Akureyri, with its century of temperature records, logged a staggering average of 10.9°C for the first 22 days of May, marking a new high for this period. Grímsstaðir á Fjöllum also noted record temperatures—averaging just under 10°C for the same duration, a record in its 119 years of operation.
Figure 2: A bar chart illustrating the percentage of weather stations that notched temperatures of 20°C or higher from May 1 to 22, 2025. On May 17 and 18, approximately 50% of stations recorded these readings. Red dots indicate the national maximum temperatures. The highest reading, 26.6°C, was at Egilsstaðir Airport on May 15, setting a new national record for May.
Figure 3: The national daily average temperature from May 1 to 22, 2025, as compared to the past decade. Overall, this May has exhibited unusually warm patterns, with only May 9 and 10 dipping below average.
New Records Set Across the Country
In an impressive display of meteorological anomaly, 94% of weather stations active for at least two decades set new May temperature records. Notably, Egilsstaðir Airport’s 26.6°C on May 15 smashed the previous record of 25.6°C established in Vopnafjörður on May 26, 1992. The record-breaking occurred repeatedly in the following days at various locales:
- Egilsstaðir Airport again (26.4°C on May 17)
- Végeirsstaðir in Fnjóskadalur (26.0°C on May 17)
- Húsafell (25.7°C on May 18)
Figure 4: Locations of stations where new May temperature records were established. The color of each dot corresponds to the day the record was set.
A History of Heatwaves
While heatwaves do occur in Iceland—periods marked by temperatures significantly above the norm for extended spans—the current heat event stands out as the most intense on record for May. The last comparable May heatwave took place in 1987, under somewhat similar weather patterns.
Significant heatwaves in recent memory, particularly at the end of July and beginning of August 2008, and in August 2004, saw similar records tumble. However, those summer heat events reached even higher temperatures, as they occurred during the warmth of late summer. In 2021, temperatures were unusually elevated, but primarily in the Northeast and East of the island. Other notable heatwaves rolled through in July 1976 and 1991, while June 1939 remains etched in history for reaching a staggering 30.5°C at Teigarhorn on June 22—the hottest temperature ever documented in Iceland.