The biggest trend with Iceland's weather is that there isn't one. Though Iceland is technically part of the Arctic Circle, it's much warmer than countries whose placements on the world map are similar. That's because of an effect called the Irminger Current – a warm ocean current that's fed by the North Atlantic Drift that helps keep the climate warmer than other northerly islands.
Like most places, the weather in Iceland largely depends on what part of the island you visit. On the whole, the southern portions are much warmer than the north, as the south of Iceland experiences a sub-polar oceanic climate while much of the rest of Iceland is tundra. Most of Iceland's population is gathered along the coasts or around Reykjavik, leaving five-sixths of the island uninhabited.
Even with these facts in mind, Iceland's weather is notoriously unpredictable. But you'll be delighted to know that, in spite of the name, not all of Iceland is covered in ice, and it experiences relatively warm and sunny conditions, especially in the summertime.
Iceland's capital city lies on the southwestern coast of the island. It benefits from its southern position in that it's slightly warmer and wetter than the rest of Iceland, but the weather can be hard to pin down.
Reykjavik's summer lasts from June to August, and is the warmest time of year with average temperatures that rest around 13°C. However, once night falls so does the temperature, regularly slipping below freezing. Because of this, it's best to become a human onion when visiting Iceland. What we mean by that is, you're best off dressing in easily-peelable layers for unforeseeable temperature shifts.
June or July is when Reykjavik typically experiences the midnight sun, though it doesn't last long. Beginning in May, the days grow so long that the sun doesn't set until after midnight, hence the name. In places like the island of Grimsey, off the northern coast of Iceland, the sun doesn't set at all for stretches of time in the summer.
Once the wintertime hits, the opposite is true in Reykjavik. The nights begin to grow longer until finally there's very little sunshine, with the sun setting in the early afternoon. Unsurprisingly, this is when temperatures hit their lowest in Reykjavik, with highs in January barely scraping above freezing and lows resting at around -3°C. However, this is when the number of tourists in Iceland spikes sharply, as more darkness means higher chances of seeing the Northern Lights.
As for the in-between months, September and October are the wettest months of the year in Reykjavik, while April and May see slight increases in temperature and relatively dry conditions.
Much of central Iceland is like no other holiday destination, completely barren and uninhabitable. It was even the site of pre-mission training for astronauts, as its volcanic appearance and conditions closely resemble the surface of the moon.
The likelihood of you travelling to Iceland's middle and northern regions as part of your holiday is low, but should you want to venture outside of Reykjavik and scale Iceland's vast terrain, there are smaller cities gathered around Iceland's northern coast as well.
While winter in Iceland's southern areas can be relatively mild, the northern regions are an entity of their own. Summer averages in northern cities like Akureyri range from lows of around -25°C to -30°C up to approximately 10°C . Even so, the weather up north also has a distinct tendency to keep people on their toes, so you just never know what you might encounter.