Unusually high temperatures

Many areas of Eastern Iceland experienced very high temperatures today (18 March 2021). The highest maxima was measured at Dalatangi, 20.4°C. This is almost as high as the Icelandic record for March, 20.5°C measured at Kvísker 29 March 2012 and the highest on the winter side of the vernal equinox. The temperature also reached 20 today at Neskaupstaður, not far from Dalatangi and was higher than 19 at a few other stations. Many local March records were broken as well, e.t. at the mountaintop station Gagnheiði, 949 m a.s.l. There today's maximum was 9.9°C, previous max at this location was 9.4°C. 

Temperatures above 15 to 16°C "regularly" occur in Northern and Eastern Iceland during the winter months - especially at stations near the ocean AND near steep mountainsides which in very windy conditions favor mixing with warm air above. 

The upper trace in the figure shows the day-to-day daily maximum temperature in Iceland from 22 September to 22 March (autumn to vernal equinox) since the beginning of regular observations. Maximum thermometer readings were uncommon before the 1930s. The last 20°C of autumn is registrered on 26 November - and the earliest 18 March (today). As seen there are quite many days which have not reached 15°C and a few are lower still, the lowest one is 29 February - with only 12.0°C - but this particular day only gets a chance every fourth year.

Dalatangi and the nearby Seyðisfjörður are the favorites for high winter temperatures, these two stations have collected 79 out of the 184 days in the range. High temperatures are also common at Seyðisfjörður during summer, but on occasions the winter maxima at Dalatangi have turned out to be the highest of the year. 

About half of the records during this low-sun period are recorded in this century (2001 and later). This is party due to the increased density of recording stations - but as the stations "responsible" for a substantial part of the whole have been recording for a long time it is likely that the general warming of the climate is also involved. The oldest still surviving daily record is from Seyðisfjörður in 1907. 

The lower trace in the figure are the daily maxima for Reykjavík - far below the countrywide numbers. 

The air above Iceland was very warm today and yesterday (17 and 18 March 2021) and March temperature records were broken at the 400, 500, 700 and 850 hPa levels over Keflavík airport - going back to 1953.