The climate in Iceland is warmer than the name suggests; thanks to the Gulf Stream, which flows past the south and east coast on its way north. The summers are cool but the winters are mild. However, the weather is very unpredictable and can change very abruptly. Good equipment and clothing is therefore essential during your holiday.
The climate is classified as being cold oceanic by the Köppen climate classification: Cfc. The island lies in the path of the North Atlantic Current, which makes the climate of the island more temperate than would be expected for its latitude just south of the Arctic Circle. This effect is aided by the Irminger Current, which also helps to moderate the island’s temperature. The weather in Iceland can be notoriously variable. The aurora borealis is often visible at night time during the winter.
The Icelandic winter is relatively mild for its latitude. The southerly lowlands of the island average around 0°C in winter, while the highlands tend to average around –10°C. The lowest temperatures in the northern part of the island range from around –25°C to –30°C. The lowest temperature on record is –39.7°C.
The average July temperature in the southern part of the island is 10–13°C. Warm summer days can reach 20–25ºC. The highest temperature recorded was 30.5°C in the Eastern fjords in 1939. Annual average sunshine hours in Reykjavik are around 1300, which is similar to towns in Scotland and Ireland.
Winds and storm
The prevailing wind direction is easterly. Westerlies are very infrequent. Generally speaking, wind speeds tend to be higher in the highlands, but topographical features can aggravate winds and cause strong gusts in lowland areas. The average wind speed peaks at around 50 mps. The average storm wind speed is 18 mps. Heavy dust storms can be generated by strong glacial winds, and can be very strong. Up to 10 tons of material can be in motion per transect per hour. These storms are very frequent in the early summer in the arid highland areas north of the Vatnajökull glacier.
There is a persistent area of low pressure near Iceland, aptly named the Icelandic Low, found between Iceland and Greenland. This area affects the amount of air brought into the Arctic to the east, and the amount coming out of the Arctic to the west. This area is part of a greater pressure system known as the North Atlantic Oscillation.
Thunderstorms are extremely rare in Iceland, with fewer than five storms per year in the southern part of the island. They are most common in late summertime. They can be caused by warm air masses coming up from the continent, or deep lows from the southwest in wintertime. Lightning can usually be observed in connection with ash plumes erupting from the island’s volcanoes.