On May 17, 2025, the tranquil waters of Eyjafjörður, near Akureyri, provided a stunning backdrop to an extraordinary climatic event. With over a century of temperature records in Akureyri, the first 22 days of May this year boasted an astounding average of 10.9°C, setting a remarkable milestone for this period. (Photo: IMO/Haukur Haraldsson)
- For ten consecutive days, temperatures soared to or above 20°C at numerous weather stations across the country.
- Numerous temperature records for May were shattered throughout Iceland.
- A new national record of 26.6°C was recorded at Egilsstaðir Airport on May 15th.
From May 13 to 22, 2025, an unusually intense heatwave swept across Iceland. A stubborn high-pressure system sat near the Faroe Islands, gradually shifting its grip over the country and pumping warm air in from the south and southeast for days on end. Conditions like this have happened before, but what set this spell apart was how early it arrived, how long it lasted, and just how widely the heat spread.
Iceland baked in warm, sunny weather that bore little resemblance to a typical May. The northeastern and eastern highlands saw temperature anomalies of over 10°C above normal, while the southern and southeastern coasts ran roughly 3°C or more above average.
Figure 1: Temperature anomalies (°C) recorded at automatic weather stations from May 13 to 22, 2025, are based on the expected daily temperatures calculated from the previous decade (2015 to 2024).
Most Mays in Iceland never touch 20°C at all. In recent years, that threshold has been crossed on an average of just 2–3 days per May. This year, temperatures cleared 20°C for ten consecutive days from May 13 to 22, plus one earlier warm day on May 7 — eleven days in total.
The heat peaked over the weekend of May 17–18, when nearly half of all weather stations in the country logged temperatures above 20°C. The national average temperature also hit its highest point of the spell during those two days.
The first three weeks of May 2025 were overwhelmingly warm. Only two days came in slightly below the ten-year historical average — everything else ran above it. At most weather stations, this May has already rewritten average records that go back generations. Stykkishólmur has reliable data going back to 1846, Reykjavík to 1881, and both saw their averages pushed aside. Akureyri’s mean temperature for the first 22 days reached 10.9°C — the highest ever recorded for that period. Grímsstaðir á Fjöllum came in at just under 10°C for the same stretch, a new high across 119 years of continuous measurement.
Figure 2: A bar chart reflects the percentage of weather stations recording temperatures of 20°C or higher from May 1 to 22, 2025. On May 17 and 18, approximately 50% of all stations documented such temperatures, with the highest reading—a remarkable 26.6°C—registered at Egilsstaðir Airport on May 15.
Figure 3: A comparison of the national daily average temperature from May 1 to 22, 2025, against the past decade (2015 to 2024). Overall, these days have proven significantly warmer, with only May 9 and 10 falling slightly below the average.
Numerous May Records Broken
New May temperature records were set at 94% of automatic weather stations that have been running for more than 20 years. The headline figure was 26.6°C at Egilsstaðir Airport on May 15, knocking out the previous national May record of 25.6°C set in Vopnafjörður on May 26, 1992.
That wasn’t the end of it. Several stations came close again in the days that followed:
- Egilsstaðir Airport registered 26.4°C on May 17,
- Végeirsstaðir in Fnjóskadalur saw 26.0°C on May 17,
- Húsafell recorded 25.7°C on May 18.
Figure 4 depicts automatic weather stations where new May maximum temperatures were recorded, focusing on those with at least 20 years of historical data. Remarkably, 83 out of 88 such stations set new May records, primarily on May 17 and 18, although peak temperatures varied slightly by region.
The longer-running manned stations add useful historical depth. Among them, the highest May temperatures logged during this spell were:
- Stykkishólmur: 20.5°C (May 17, 174 years of data),
- Grímsstaðir á Fjöllir: 24.0°C (May 15, 119 years of data),
- Litla-Ávík: 23.3°C (May 17, 31 years of data).
Reykjavík recorded its second-highest May temperature ever at 20.3°C, beating a mark that had stood since 1960. Akureyri reached 24.2°C on May 17, stopping just short of its all-time May record of 24.6°C set in 1980.
Figure 4 highlights the locations of automatic stations that set new temperature records during the May 2025 heatwave, with color coding indicating the days on which those records were achieved.
Historical Heatwaves
Iceland has seen heatwaves before — stretches of several consecutive days with well-above-average temperatures. But the May 13–22, 2025 event is the most intense ever recorded for the month of May. The last spell that came close was in 1987, driven by remarkably similar atmospheric patterns.
More recently, notable heatwaves hit around late July and early August 2008 and again in August 2004. Both periods broke records of their own, with temperatures clearing 20°C over several days running. It should be said that those earlier events produced even higher peaks — they were happening in midsummer, not spring.
Summer 2021 brought noticeably elevated temperatures too, though that heat was largely concentrated in the northeastern and eastern parts of the country. July 1976 and 1991 also saw significant warm spells. And then there is June 1939 — when the mercury at Teigarhorn climbed to 30.5°C on June 22, the highest temperature ever recorded in Iceland.
