The amount of sunlight hitting the Earth’s surface is affected by the tilt of the Earth and its atmosphere.
The Arctic is sometimes called the land of the midnight sun. North of the Arctic Circle, the sun does not set for a period of time during summer, called polar day . This happens because the Earth is tilted on its axis. The length of this period of continuous daylight depends on how far north of the Arctic Circle you are. At the Arctic Circle, there is only one day of continuous daylight. This occurs at the summer solstice, usually around the 23rd of June. At the North Pole, there is almost six months of continuous daylight. The sun rises close to the spring equinox, around March 21, and does not set until the autumn equinox around September 22. In between the North Pole and Arctic Circle, the number of days of continuous daylight decreases as you get closer to the Arctic Circle. In winter, the North Pole experiences six months of continuous night. The number of days of continuous night also decreases the closer you get to the Arctic Circle. At the Arctic circle there is one day of continuous darkness.
The dynamic climate of Iceland
“If you don’t like the weather right now, just wait five minutes,” people sometimes say in Iceland. This is an indication of the strong variability of the Icelandic climate, where one may occasionally experience the four seasons over a day: sunshine and mild temperatures; windy, cool temperatures and rain; snow and temperatures below zero degrees C. When this happens (rarely), it is an expression of the location of Iceland at the border between Arctic and temperate seas, and between cold air masses of the Arctic and warm air masses of lower latitudes. Ocean currents and sea temperatures – Iceland, located at 63-67°N and 18-23°W, has considerably milder climate than its location just south of the Arctic Circle would imply. A branch of the Gulf Stream, the Irminger Current, flows along the southern and the western coast greatly moderating the climate. The cold East Greenland Current flows west of Iceland, but a branch of that current, the East Icelandic Current, approaches Iceland’s northeast- and east coasts. This is reflected in the coastal sea surface temperatures around Iceland. They are generally close to +2°C during the coldest months (January-March). Sea temperatures rise to over +10°C at the south- and west coasts of Iceland during the summer, slightly over +8°C at the north coast, but are coolest at the east coast where summer sea temperatures remain below +8°C. During years with heavy sea ice off northern Iceland, sea temperatures during summer can remain close to winter temperatures.
Read more here https://notendur.hi.is/oi/climate_in_iceland.htm